The radiator doesn't need to be made of copper as far as I'm aware.

We've just had a Stratford stove and backboiler fitted to do our domestic hot water and central heating (4 radiators + one as a heat-leak). You just have to make sure that it has a high-enough BTU output - for the Stratford our's had to be a minium of 10% of the stove's output (45,000BTU's for ours) and it couldn't have any sort of valves fitted.

We've had the tank installed in our bathroom as it's a gravity system and were advised that given the room height in our house it would be inefficient trying to get the cyclinder into the attic. After struggling to find a suitable radiator with high enough output I found a great vertically mounting 'old-style' iron radiator rated at 6000BTU's from a plumbing company near us in Sussex and it's mounted on the wall next to the airing cupboard. It should heat our bathroom and our bedroom at the same time.

Given the cost of replacing our copper cylinder I would have thought that a copper radiator would be prohibitively expensive. I think ours cost approx £100.

Hope this helps.