If you buy "customer" Recaros from demon tweeks and the likes, you basically get a flat bottomed seat, to which you buy the runners for your car from Recaro. So that means you can buy the seats and swap the subframes between many cars. The Clio Recaros have Renault bases/subframes, so they only fit Clio 3.
I'd have thought Vauxhall would also use a manufacture spec base / frame, however not 100% sure. I Remember Honda using Recaro trendlines in the accords which were customer spec, so with them you could buy Clio subframes, and they'd bolt straight in.