Thanks for your replies folks, and for the link [MENTION=173992]non-fixie[/MENTION]
I've emailed the company (or whoever operates their website) to see if I can glean any more info on the frame. In the meantime, it's going to be a case of cleaning it up and test-riding it. Really looking forward to trying it!
[EDIT] just as I clicked post, an email arrived:
...Certainly worth restoring. It has been refinished at some stage with a very thick paint. I think this will have filled in the impressions of the frame number. It will almost certainly be repeated on the steerer tube, which will mean taking the forks off but the number will be very obvious. Hope this helps, Kind regards...