Hannah if purchased from a trader you have every right to get your money back, if you're unhappy with the car, or feel it was wrongly described.
Another option is to contact VOSA re if you believe the MOT is 'dodgy', but you shouldn't have any of the worn or damaged item replaced in the mean time.
The car may be a rough diamond that requires some remedial work to get it up to standard.

Some years I take my same car to the same MOT station, with the same tester, and an advisory i got last year suddenly doesn't get flagged up the current year....... but I'd like to think anything dangerous would be highlighted.