The group began meeting here each week around three years ago when McGrigor began learning ukulele and wanted to find people to practise with.
"I was inspired by the ukulele festival. Once you get addicted, you start noticing ukuleles everywhere," says McGrigor.
Not least of all are the colourful ukes replacing the dreaded recorder in many school halls. When I was in primary school, we struggled (along with our parents' sense of hearing) to learn Three Blind Mice on the portable, chuck-it-in-your school-bag recorder.
As Mike Dickison, author of Kiwi Ukulele: The New Zealand Ukulele Companion, writes: "Do your kids a favour and get their school to switch to the ukulele. Yes, it will teach them chord theory. Yes, it will teach them singing. But, mostly, it doesn't make an awful piping shriek ... It will also make everyone smile.'
Dawn Claydon, a hairdresser by trade, strums next to me on an elaborate azure ukulele with inlaid abalone and mother-of-pearl dolphins swimming around the sound hole. She says: "People crack up when I tell them I play the ukulele, but it's great as it makes your brain work."
Each week there are different people in the room; some are regulars, but others just pop in when they're in town - there are even some accomplished musicians mixed in with the beginners. The atmosphere, a true music-lovers environment, must be hard for even the most experienced ukulele player to resist.
McGrigor, Claydon and Linda Taylor stand at the front of the room, calling out chords of songs they've forgotten sheet music for. Everyone follows their lead from the comfortable seats.
One of the members, Rob, puts another log on the fire and the group play The Beatles' I'll Follow the Sun, as we head out into the crisp night air in total darkness to feel our way down the stairs to our car, parked on the edge of the steep drive to the Mt Victoria summit.
Actor Sam Neill once wrote on Twitter: "A route to happiness - learn to play a ukulele. Always makes me unreasonably cheerful. Aloha..." Judging from tonight's performance, I'd say he's probably right.
More info
* The Devonport Folk Music Club has a ukulele jam on club nights. It's free, but if you stay for the club night afterwards - where musicians perform two numbers each in a kind of intimate variety show - it's $3 members, $5 non-members. The venue is The Bunker, which started life in 1891 when it was built as a command post to watch for a possible Russian invasion. The Bunker is on Mt Victoria, off Kerr St, Devonport.
* Learn the basics first with Kiwi Ukulele: The New Zealand Ukulele Companion, published by AUT media, $24.99.