Hyperion.uk said:
first time in just over 20 years that I will own a private car
At the risk of telling you things you already know here are some thoughts:
As [ref]raymond.harper[/ref] says, check the MOT. You can get a lot of detail from https://www.gov.uk/check-mot-history. I'm always a bit concerned if something is on the MOT for multiple tests in case someone didnt bother taking care of the car properly.
Take a torch and be sure to get on the floor and look under the car. I went to see one pristine looking car and there was terrible rust on all the exposed metal underneath (chassis, suspension, exhaust). Reach your arm under the car with your phone to take photos of hard to see spots.
Ask them not to drive before you visit so that you can hear what its like on a cold start with the bonnet open.
Get them to take you for a drive as it might show you how they have been driving it and what sort of life it has had.
Use one of the websites that can give you history of the car and check for things like theft and write-offs.
Ask them if you can test drive it if you buy the appropriate 1 day insurance before hand.
Ask if there have been any modifications at all and if so would it come with the original parts so they can be refitted if you want.
Take a note of what tyres have been installed and if they match, size and make/model.
Check under the bonnet and under the car for any sign of oil leaks.
When you get in the car press every button you can find and make sure it works. It feels silly doing it but any decent seller wont mind and its worth finding problems before hand.
Check the carpets in the cabin and boot carefully for any sign of damp in case there have been leaks in the past.
I'm not sure if a 3.0si is the same as the Z4M in this regard but heres some other things I was advised to check when searching for a Z4M
Check the service history for the "Inspection 1", "Inspection 2" and "Oil Service". Ideally these will have been alternating in the service history.
Does the 3.0si have a vanos? If so, see if it has been replaced.
Importantly, dont be scared to walk away. There are always cars coming up on the market so if it doesnt feel right then keep searching.