In the end, I chanced on one from Serck Services - an alloy one that was never collected after ebing ordered and I got it for £200. The only downside was that the exits from the rad were at different angles so I had to change the pipes around a bit!
I managed to hget a slightly damaged one (only the fins which you can't see anyway) and it's been fine for £200 + VAT. Otherwise I'd have gone for a recore.