I'm planning on the MGB option, only problem is that MGB seats, well look like MGB seats! maybe because I had one for many years.
I have found someone on Ebay who does a set of "hump" leather seat covers for £275, they don't quite look as MGish as others.
And seat rebuild kit for £54 + Vat
Most sellers on Ebay are after £45 just for the "hump" seat foam.
I picked up a pair of seats for £35 for the pair.
I intend to fit them to the existing base and transfer the heated seat elements. I don't know if it's going to work as I'm still waiting to get the car back.
I did look at the Ford KA leather seats as option, cheap a s chips, you can get a good pair for less than £50. I'm not sure if the shape will work but at that money it could well be worth a punt.
MGF seats also look good, there was a blue car on the forum that had a cream pair fitted that looked very good but around £350 for a good pair. Alfa Spider seats also looked as if they could be an option.
I think the Rover seats just look too big.
I would be careful about fitting any kind of seat that does not have any back adjustments, they can prove to be very uncomfortable.