Good evening,
I am not at all sure if I am correct, but I thought that the 1983 Clubman had Campag 980 gears and shifters, and the 1984 (and 1985) model went to Suntour and if the S in the frame number does mean December then it would seem reasonable for such a late 1983 frame to be built to 1984 specs.
Given that the OP has said that the bike is almost as it was from the shop then the pedals are interesting, in 1985 the law was changed to require pedal reflectors. Whilst the original owner could have added them it seems quite possible that a retailer still had a 1984 model in stock in 1985 and added them themselves.
The
eBay link from ChrisS seems overpriced to me, it is a Reynolds SMS tubing frame which is a non-alloy (hi-tensile) steel, at least the OPs is butted 531 main tubes.
£50 was a bargain and I agree that it
could easily fetch Gunk's estimate but it may take quote a while for that buyer, on a 7 day listing, collect only I could easily see it fetching £75-£150 and being bought by someone who plans to resell it or someone who just wants a bike.
The condition appears to be wonderful but it is still a 36 year old bike and it is not clear if anything like the bars, seat post, cables or chain have rusted up, 531 main frame tubes only with non-alloy steel stays and forks is a solid entry level enthusiast's bike but it is also a long way from being sell the children as I must have it.
You mention it needing new tyres, add to that an eBay buyer paying say £30 carriage on top of £250 and that starts to look expensive.
Bye
Ian