Fitting rear bench seats

Ive bought them on eBay and they are a folding A-frame with a bolt hole on each end-are they really just bolted with 2 bolts to the wheel arch? Or is there more too it?

You really need to use a load spreader under the wheel arches - a metal plate which you drill and bolt through will do the job. The arches themeselves are not strong enough to take the laod in an accident.

Soem seats also have the rear bolt/screw through the capping (think that's the name) - the metal horizontal section that goes between the sides about 1/3 of the way up

usually they bolt through wheel arch and you put strengthening plate on underside ie 2" x 4" and back rest of seat has brackets with a tang that pushes up into pre-existing slots on underside of capping