I thought I'd better post this up so someone doesn't have to go through what I did!
The radiator on my E46 325ti was bowed, so off I popped to Euro Car Parts to get a replacement. I bought the cheap one, and then set about replacing it. It fitted with a bit of fettling, then it transpired it had a leak from the bottom. I looked this up online and found that it was supplied only with the automatic valve, and not the bung for the manual! Being new to the e46 (had the car 3 weeks!) I wasn't aware of this, until finding the following thread:
I spoke with ECP on their internet chat thing, and showed them the above link, they checked their stock and none of this model had both options! So, they are hoping to rectify this situation asap! In the meanwhile I got a Nissen radiator from them, and it fitted fine!
ECP were more than helpful, but check the radiator has both variants before installing!