I edited a photo of the relevant part of the bike into the question, but then decided to answer it. I can't find a photo showing any more detail than that, sorry.
The two weld bumps on the right hand seatstay will be where the the frame joiner has been put in, and resumably there's a bolt or two in there, but I can't find out, sorry. OTOH, it will almost certainly be easier to open that up than to find a replacement belt, so I wouldn't worry about it. It will definitely not require welding to do that, though.
This search for "belt drive frame joiner" produces a lot of hits, including an image that looks as though it could be the device used in that bike.
Image from road bike forums where there is a thread discussing how that device was installed in a frame. If it was turned so the bolt heads were on the inside of the frame, it could look like the Novara Gotham. Or they could have an equivalent design.
I'm looking at the gap between the welds above and I think there's a faint stripe in a slightly different colour, suggesting a centimetre wide chunk gets unbolted from the seat tube. But it's very, very faint.