Having helped to lift the lid on his industry in the Channel 4 series Posh Pawnbrokers, which followed life at his shop on London Road in Sheffield, Dan has turned his attention to the British passion for collecting in a new one-off TV programme, Collection Hunters, which airs on Saturday.
"We found lots of people were coming to the shop and not just wanting to sell to us; they were also trying to buy items from us. They wanted us to locate things that ultimately would complete their collection. I started thinking 'There seems to be a business in this'."
Dan established what he believes is the UK's only specialist service of its kind, scouring the country - and sometimes beyond - to find the missing pieces needed to achieve a whole set of any item, from tax discs to toy soldiers.
"We deal with luxury cars a lot, and tea services," says Dan. "One lady even wanted us to complete her cruise ship ashtray set. Back in the 80s and 90s they were all branded with the cruise logos. She was just missing an obscure one from an Italian line."
It was an enjoyable sideline - so enjoyable, in fact, that he was deriving more pleasure from it than his normal trade buying and selling valuables. "To date we've completed over 100 people's collections. We're like old-fashioned detectives, really. You name it, someone's collecting it."
The new programme came about when Dan went for dinner with a producer from Posh Pawnbrokers, and told him about his latest venture.
"He said 'Why haven't you told me about this before? It would make fantastic TV show'. It didn't cross my mind, really. I had no involvement in pitching it."
On Saturday viewers will see Dan getting to grips with Lambretta scooters, a coffee service and a hoard of obscure Soviet furniture that 'doesn't look like much, but is worth an astronomical amount'. A 'fascinating' set of 50p pieces also features, he says. "When we were filming that, the first thing I did was thrust my hand into my pocket to see if I'd got the missing 50p. These pieces are supposed to only be worth 50p, but they're worth hundreds of pounds."
Dan, who took over London Road Jewellers & Pawnbrokers 10 years ago after a spell in recruitment, is accompanied on screen by auctioneer Gary Don, antiques dealer and former Big Brother contestant Mandy Longworth, from Doncaster, and Debbie Ellis, an expert in vintage wares.
Normally, once completed, the worth of collections increases - one contributor's doubles in value from Â£20,000 to Â£40,000. But Dan won't say whether anyone chooses to sell.
"That's for you to see on Saturday. Sometimes people's collection is, in effect, their lifetime's work, but when you're faced with a large amount of cash, are you going to give it up? Sometimes they do, sometimes they don't. It's a very hard decision."
What is behind people's urge to collect?
"It's a question I ask myself on a daily basis, and I've yet to find the answer. I can come across someone who seems very meek, and then they start talking about their collection, and you see this passion and fire you didn't know existed in them. That is exactly what collecting is about - that exhilaration and excitement. Bringing a sense of completion; in themselves, sometimes, as well."
There isn't a plan for more episodes yet, and Posh Pawnbrokers isn't poised for a comeback either, though Dan would 'never say never'. "I did 60-odd episodes and I worked on it for a very long time. It was exhausting towards the end. I needed some time to chill out. I know it's been extremely popular, especially in the city, and a lot of people have asked about it."
Dan is, however, working on a new reality TV show with his sister Cherise, focusing on 'escapades' at their Stylebar salon on Ecclesall Road.
"You can expect lots of arguments, and ups and downs. But most importantly, we're going to make Sheffield look as glamorous as anything. There'll be lots of tears and tantrums."
Collection Hunters is broadcast on Saturday, May 5 at 4.30pm on Channel 4