Hi Bernie,
Many thanks for all of that, and I do appreciate that I am at risk of solving a symptom rather than the cause. I did notice that the amount of coolant I put back in the other day was well less than what the haandbook says is the capacity, but I put that down to air pockets etc & that it would “settle”. But after ~400 miles it hadn’t. The thought of clearing out the block is horrible, but a new core on the radiator could at least help. (The engine is original).
Are there any obvious outfits that can re-core / replace my radiator? (1956 11B, Paris built)?
Many thanks,
Julian