Tim kindly started this thread for me, so I should report back. I opted for MGF seats on the basis of the classic look of the MK1 seats and the reasonable cost/availability. Plus fitting was simple per the easy to find guide (from Adam in NZ for tssc?).
We're really pleased with the results. Can't recline past the B pillar, but sliding forward to allow enough recline still left our legs comfortable. We each had one good solid 2hr sleep per night on RBRR, and it was probably adrenalin and minor car/route/event issues that prevented more.
Re height: I've used the mgf runners. The seats do sit a little higher but not much, and we didn't notice it while driving. We did notice that being wider we're slight further over toward the door, making the steering wheel sit to our left. Soon forgotten.
Photo below gives an idea of height difference. On the side-by-side photo, the vitesse seat is without runners, the mgf on its runners but with the 4 corner fitting brackets cut and ground off.