What bike have I bought? Can anybody help me identify this bike? It's a Claud Butler with Reynolds 531 steel - that's all I know.
This is a standard English manufactured sport bike probably from the mid-60's. 

It used freewheel type hubs and from what I can see you appear to have modified the rear wheel with a seven speed freewheel. The original rear triangle spacing was probably 125 mm and the seven speed uses a 127 mm spacing. Usually someone would re-space the rear triangle and put a spacer on the right side of the axle and normally they would not re-center the rim. This would cause the wheel to be slightly off-center in the stays. It usually had no deleterious effect.12speed