We do all our uprated rads for the Anglia boys, aswell as other Old School Ford, in Copper and brass and they work fine.
The beauty of them is they are around 2.5 times cheaper than the equivalent ally rad and they can be repaired if they get holed, whereas an ally rad is basically scrap.
The downside is they weigh a tonne.
However, in saying that, my 2.0 Zetec Anglia runs a 1.0 Polo rad, in ally and its mega efficient and I dont get any overheating problems at all.
What some people are doing now is buying a modern rad with the plastic tanks and then having ally tanks welded on the ends to give them more strength and to suit different applications and that seems to be a nice cheap way of getting an ally rad.
But if anyone needs any copper and brass stuff doing we can help.