This is proving to be a right pain!
On a whim I called the dealer, who surprisingly quoted me £140 for an OEM radiator. I went to collect this morning only to find that this one had not only the fan mountings the wrong way around, but the transmission cooler lines were on the wrong side as well! They were insistent that the part number was correct, and even called the technical help line who told them that it was the right part.
They were completely stumped when I then told them to compare it with my XJ which was parked outside.
Anyway, I've taken your advice Jonny: the ones from RockAuto are the only ones I've seen that actually have the correct picture, so I've ordered one from there. I've gone for a Spectra one as the consensus in the US seemed to be that they're of good quality, and often made in Canada rather than China.
So much for getting this sorted quickly, but hopefully this will at least be the right one!
I've got a couple of days without the XJ now anyway as it's off to Peak Jeep tonight for a few bits that I'm too lazy to sort/investigate.