LondonClassic
Retro Guru
I think its going to stress the top of the seat tube and flare it further open if you used a quill seatpost.Do you think I could get around it using a wedge/quill seat post or would that be a bad idea?
I would try Winston Vaz (Varonha Frameworks). He lists seat lug repair as one of his services. A whole new seat tube from £160. Of course you're going to need paint after that. His brother Mario (works upstairs from him) might be able to help there...not sure if he retired though. Both of them worked at Holdsworthy in Anerley and Winston worked for Roberts also.
Worth sending him a pic and asking.