Tanned from the recent heat wave, and dressed in casual shorts and a shirt, there's no hint of attitude. No subject is off limits, and all because the 48-year-old East Lothian-based prog-rocker is clearly a contented man.
Lounging on the outsized sofas in the bohemian living room of his impressive Haddington home, containing record players, state-of-the-art music systems and countless records, a relaxed Fish laughs at his ever-growing DVD collection.
Meet The Fockers has clearly been recently watched. As has Lee Evans. And then there's Love Actually. It all seems a bit soft for the man who once sang about being an "orphan of heartbreak, disillusioned and scarred, a refugee," and who was left devastated by divorce from his former wife, Tamara Nowy, five years ago.
The answer to his new-found happiness soon joins us in the living room - 29-year-old Heather Findlay, a pretty, blonde singer with the band Mostly Autumn.
"Derek is a gentleman. He's very caring and good-hearted," she enthuses.
"He cares a hell of a lot for his daughter and that's very impressive. The Derek I know is the kind man who loves his garden."
Heather and Fish (real name Derek Dick) met at the glitzy Classic Rock Society awards in December and they've been together ever since. "I knew he was going to be presenting the awards and I knew of him," admits Heather. "I had actually met him in 2001 but he didn't remember me then!
"I got talking to him afterwards as I was talking to his daughter Tara about the music she likes. Before I knew it Derek was asking what I was drinking and it just went from there.
He told me to call him Derek, which is great because that's how I know him. Fish is a different character from Derek, it's his alter ego."
It's clear Fish is equally smitten. "I was wary of being drawn to someone in the industry," he admits. "But I've been in the situation before where I've gone out with people not involved in music and they've not understood my career.
"When I met Heather, I wasn't looking for romance at all. In fact I'd become attuned to living on my own." But the pair immediately hit it off. And her presence has clearly affected Fish for the better. "Oh yeah, I'm happy," he smiles. "I'm happy with my lot. It can be difficult when it's two singers [dating]. It's about making the time together whenever you have a break. But it's going well."
And so is work. "I'm enjoying what I'm doing and I'm lucky in that I've got a loyal fan base and I can continue working," smiles Fish. "I'm not in the 'music industry', which I'm glad of - I'm just making music.
"The business has changed so much and I would hate to be in a young band trying to start out now. The demand to compromise is very high."
Fish is clearly disillusioned with the music industry, and has been since his departure from Marillion in 1988. But he still loves music.
"I fell in love with it as a kid, but I started late as I begun at 21 because of a lack of confidence and opportunity. I just left Dalkeith High and I didn't know what to do."
After a couple of unsuccessful auditions, Fish struck gold with Marillion in 1981 after seeing an advert in Musicians Only magazine. The band signed to EMI in 1982, but by 1988 Fish had had enough.
HE recalls: "The reasons were a mixture of musical differences - I detested the management we had, and we had a number of unresolved issues. We were playing on average to 10,000 people a night five days a week, and it became a big machine . . . and machines aren't good with people.
"I decided to jump ship. I was impetuous at the time and in retrospect I could have done things differently but I had to get out. It was affecting my personal life."
He continues: "For example, we played Paris in an 18,000-capacity venue. I was taken straight to the venue and stayed in a small room all day doing interviews. We weren't allowed to leave, then we played to the crowds but we didn't see them because of all the lights.
"Because I didn't start singing until I was 21, I was a fan [of bands] before I became part of one. But with Marillion there was no human contact with the audience. There was a lot of soul and spirit being lost, even in the writing.
"There was no inspiration but the record company didn't care."
And so Fish left, returning to Dalkeith, before moving out to a farm in Haddington where he developed his own studios. A year later he was a solo artist, doing his first gig in Lockerbie.
"It was frightening, really scary, going solo. I'd gone from rehearsing with my mates and playing to 18,000 people. I've never been as successful numbers-wise as Marillion but I've had a lot more fun and done a lot more things."
But being a performer has its downsides. "It can be very, very lonely on the road. People get the impression it's always hotels every night but the level most bands are at, it's more buses."
Fish is certainly no longer lonely. And along with regular visits from Heather, who currently still lives in York, Fish is now a full-time parent to his 15-year-old daughter, Tara, who moved back last year.
"Tara moved over from Berlin where she was living with her mum because of a combination of circumstances and schooling," explains Fish. "It's great having her here. It's very scary though and she teaches me a lot. But we've always had a really good relationship and I have enough liberal attitudes so we don't have too much conflict."
When his marriage broke down, Fish was on the brink of bankruptcy. He was forced to sell the main farmhouse in 2001 and live in a smaller house in the grounds. Since then he's worked tirelessly to support his daughter, releasing albums, touring, acting in TV hits such as Rebus, The Bill and Taggart, taking part in Celebrity Weakest Link, and even landing a role in Hollywood movie, The Jacket.
"I'm a single parent and I'd come from the edge of bankruptcy working my ass off to provide for her and give my daughter security. So when this is threatened . . ."
He breaks off. The "this" he's referring to is the fact that his former PA Kim Waring, who worked for him for four years running the fan club, fulfilling orders for CDs and daily office administration, allegedly stole 68,000 from his accounts while he toured.
After his accountant pointed out the massive hole in his finances he took his former employee to court, and in December 2005 he was eventually awarded around 170,000.
"I'm a creative artist not an accountant so I was at the mercy of others. It was pretty bad. I didn't realise when the money was coming in, it was coming to her. So she betrayed me. Me and my daughter. That money was to give my daughter security. So she was f*****g with my family too."
Now Fish is looking towards the future. And that means the release of his new CD Return To Childhood, which marks the 20th anniversary of the acclaimed Misplaced Childhood album.
"The whole idea generated from a fan club convention we had in Holland in 2001," explains Fish. "We'd had a few wines too many, it was 2am and we were thinking, what are we going to do? Then we thought, why don't we do one night of Marillion and one night solo? And it was brilliant."
And in 2005, for the first time in nearly 20 years, Fish performed Marillion's Misplaced Childhood in its entirety during his European and South America tours. And it seemed apt to record one of the concerts for posterity. The result is a nostalgic concert of two halves - solo Fish classics and Marillion hits.
So what's the future for Fish after his next tour? "To be happy and enjoy life . . . and continue to make music."
Return to Childhood is released by Snapper Music on August 21. The Fish Convention takes place in Haddington from August 25 to 27. For tickets log on to www.the-company.com or visit The Plough, Tyneside Tavern and Kelsey's Bookshop in Haddington