Re:
I enquired and the seller kindly sent me some pictures.
He said the serial number is WG... with some digits hard to make out - he took a picture of the underside.
He said £180 shipped to London for the complete bike.
It looks quite in need of TLC and has quite a bit of rust, the components are also iffy in condition, and I'm not sure the £180 is worth it -to be honest I'd rather just the Frame and Forks as I think it'd look nice as that blue is very catching.
Anyway, I at first thought it was a Competition, but it seems to be a Clubman as said before here by those with better knowledge than I.
It has that braze on gear cable thing on the stay.
here's two pages from 1977 Catalogue, followed by pictures of the bike.
If it was a Competition I may have been more tempted, as it is I will pass.