I’ve simplified the whole situation by not buying the car. I didn’t think was worth the bid that had already been placed on eBay so walked away.
I have actually agreed with a seller before that he owned the car, hence it was still taxed and insured (3rd party via my insurance), until I got home, though it was a friend of a friend so there was more trust. I probably wouldn’t risk it with a stranger.
Having said that, you’re not automatically liable for anything that happens to a car still registered in your name (which doesn’t confer ownership), or even one you still own. If you’re partner gets a speeding ticket in your car, you don’t (or shouldn’t) get the points. It could get very messy though.
Anyway, I’ve avoided the whole situation for now. Instead I’m dealing with taking a bike on a British train. Two of my pet hates in one day 😀