It doesn't help with that new problem, but opening the bonnet won't tell you which engine as they are both the same to look at. The difference is in the program in the ECU (Engine Control Unit), so the only real way to know is to use a T4.
Thanks for all the replies. the car was advertised as a CDT, but listed as a CDTi on the V5. I'd be quite pleased if it turned out to be a CDTi after all, as that's the one i really wanted in the first place. I'm in Grays, Essex. T4 anyone???