So after some basic online research it turned out the bike had likely been dropped, as its current colour wasn't what it left the factory with or what the DVLA had registered. I also did a full history check by texting BIKE to 83600 (only cost £3.10) and the bike came back clean (so no cat D etc.)
Then after getting a bunch of photos of the bike it was evident that the bike had been also recently dropped (yes, again, but minor), as it turns out by the father of the current owner (bent tail tidy, twisted non-std indicators, scuffed can, bent gear lever, scuffed bar end). I made an honest and genuine offer for the bike, which was reduction from the original price to cover all the bent and scuffed bits I would have to replace. That and I would need to inspect the frame to check there was no damage from the previous accident etc. Its been 2 days and no contact.
Fair warning to anyone else that might come across this bike - it was listed on FB, registration starting SP07.