Thanks for all the info.
I ended up not buying it though.
The guy started it before I asked.
I did all the usual checks and it seemed to be fine.
I went to restart it to check reversing on lock; starter motor went like a good 'un but no ignition.
Fuel pump seemed to be working though.
The guy said it was probably out of fuel (it was reading low but not empty) so he shot off to get some, but it didn't make any difference.
Finally after mucking about with the central locking because he suspected the immobiliser, he locked both keys in the car. Game over.
I'll keep looking...