The actual differences are difficult to determine by registration letter or year, as some up to 2000 and 2001 onwards were cross sold over different registration letters.
The easiest way to tell as by the front indicator colour. If the front indicators are orange, then it's a pre 2001 model, so would have the 2.0 L series diesel and manual 5 speed PG1 gearbox, or 1.8 K series petrol engine, again with the PG1 5 speed gearbox.
If the front indicators are clear, then it's a 2001 onwards model.
There were extensive differences made to the post 2001 models, the largest being the replacement of the L series diesel with the BMW sourced TD4 2.0 diesel engine, fitted with a Getrag 5 speed manual gearbox, or optional 5 speed Jatco automatic. The KV6 was introduced at the same time, supplied with the Jatco 5 speed automatic.
There were loads of other changes made to the body, suspension, steering, and safety systems, as well as more electronic integration such as ABS/TC/HDC becoming standard equipment and cruise control being optional on the automatic models. Things like the heated front screen and power fold mirrors become optional, or standard depending on specification.
