CHEAP TRAILER TO CARRY A 7, 2 OR 4 WHEEL,

What do you call cheap?

DEPENDS WHAT IT IS.

I'm struggling to think of a vehicle with 7 wheels, never mind how much
the trailer to carry it costs

I have a Hazelwood (similar to Ifor Williams) plant trailer soon to be for sale. It has a solid floor, dropdown tail/ramp and the bed is 6'x10' (dunno how big your car is).
Twin axles with all new brakes and bearings. Fully rewired and new lights all round.
It will soon to be on Ebay with a reserve of £600.
Although I'm a long way from you, this may give you an insight as to what you can expect to pay!! HTH!

dilley u have U2U

I have been watching this to see how much it makes, just out of curiosity.