He quietly introduces himself, takes a seat, and leans back resting his bald head on the sofa cushion, much like you would in a therapy session. But it's unlikely that Hill (or Matthew Hall, as he was born) is interested in cathartic chit-chat, he's simply exhausted.
"I'm always having ideas that I write down in a little book. Most of the time I can't persuade anyone to put any money into it but every now and then, like this year, I've had two crazy ideas that I actually got people to take seriously," says the 49-year-old.
The first big gig is I Can't Sing! The X Factor Musical, which he's been developing with Simon Cowell and is confirmed to be opening in London's West End in early 2014.
"It's been ready for a long time. We're just fine-tuning it, really. It won't be until we get into rehearsals that we find out what works and what doesn't."
The second project is The Harry Hill Movie, which marks a much longed-for leap from the small to big screen, "a dream come true".
Hill came up with the idea as TV Burp - his hit show which raked through the week's TV, digging out amusing blunders or inserting hilarious innuendos into scenes - reached its conclusion in 2012.
Given his taste for surreal humour, it should be no surprise that The Harry Hill Movie exists in a heightened world.
Julie Walters plays Hill's rapper Nan: "I thought there's no way she'd say yes, but getting her helped us a lot with getting the rest of the cast. People love Julie and it makes it more like a proper film, rather than something that's straight to DVD."
Sheridan Smith also stars. And as for the plot, it sees Hill taking pet hamster Abu (voiced by Johnny Vegas) to vet (Simon Bird), who wrongly diagnoses him as terminally ill.
Hill then incorrectly translates Abu's dying wish to be a trip to Blackpool, and the trio head off to the seaside resort. Hot on their heels is the vet, who's actually the henchman of Hill's evil twin brother, Otto (Matt Lucas), who has his sights on revenge for being left to be brought up by Alsatians. Much silly, anarchic family fun ensues. There are even a couple of musical numbers.
He doesn't deny that the movie provides a peek into the workings of his mind. "I think a lot of comics have a unique world," he says. "People always say it's surreal but to me it's silly, a bit like The Goodies, or maybe Monty Python. That British thing of talking puppets and so on."
Hill has a string of accolades, including British Comedy Awards and Bafta gongs, to his name, and his popularity is testament to the fact that his humour is universal.
"It's instinctive. I don't have to rein in a tendency to be rude or dark, it's just my sort of shtick," he says. "When I first started, I used to swear a bit but it wasn't funny."
Not that he has a problem with edgy humour. "Some of my favourite comedians are Micky Flanagan, Sean Lock and Stewart Lee, and they're quite near the knuckle at times. But you have to be true to yourself."
Born in Surrey, Hill lived briefly in Hong Kong before settling in Kent, and famously studied to be a doctor before deciding to give stand-up a go. But after winning the 1992 Perrier Award for Best Newcomer at the Edinburgh Fringe Festival, he never looked back.
"A lot of it is confidence, and that [award] was a big turning point," says the star, who recalls encountering a young Matt Lucas on the circuit. "I saw him years ago. He was about 17 and it was immediate to me that he was immensely talented."
Lucas has talked of the great help Hill was in those early days, saying: "When I was starting out, he was very kind and gave me lots of phone numbers of people who were running clubs and said, 'You can call these people and tell them I said to book me,' so I owe him big time."
As for Hill feeling any pressure about his forthcoming projects, he's as unperturbed as someone with two decades of experience can be.
"I never go into anything thinking about that. If you're a comedian, you put your neck on the block every time you go out. You have to be thick-skinned."