Can a dealer offer me less for a p/x after agreeing a price?

I have picked up a new car and dealership agreed price for my part ex. I have had the car nearly two weeks and they have said it looks like the service history has been altered for my old car, not by me...

What used van do you recommend for £8000?

I'm looking at buying a Toyota Proace, Peugeot Expert or Citroen Dispatch (around three years old). It’s for my business, but will also need to tow my caravan. Is the 2.0-litre Proace the better option...

Should I buy a used Lexus with a gap in the service history?

Should I buy a 2017 Lexus which has five Lexus dealer services in the record although there's a gap of 3 years? The car is being sold by a Lexus dealer.

A van I'm interested in buying is priced lower than expected - should I get an RAC inspection done?

I'm looking at buying a van and have narrowed it down to either a Ford Transit Custom or Mercedes-Benz Vito, on a 13-plate with good options. I want it to tow my caravan, but I've been told the Vito sits...