Hell Ashleigh,
I’m sorry to hear of your on-going issue, but to be honest, I’m not at all surprised, and although my reply isn’t going to help your case, it may well serve as a deterrent to others who may think about following the same line of purchase.
As I see it, the dealer should have sorted out the U.K. registration before (in caps) advertising the car for sale.
In your case he has ‘got away with it’ by not completing the necessary involved work before selling you the car - without U.K. title. You are now realising that this is a rather involved process which depends on your (in caps) effort to sort out.
Moral:- never buy a vehicle without a U.K. V5.
I’m sure you will sort it eventually, but this responsibility should not be yours.
Good luck and kind regards,
Gareth.