Hopefully you can buy the underseat looms (including fuse holders & relays) + operating switches, switch panel & centre console from the person selling the seats.
If you're good with a dremel , you could probably cut the holes for the switches in your own console but you'd need to make a template first.
If not, you need to contact someone who breaks D2s who may have the parts.
As Sierrafery says, you'll need someone with a Nanocom, Hawkeye or similar to then enable the electric seats option in the body control unit (bcu).
I was fortunate & the guy I bought the seats off did it all for me (very good guy called Heathy off the D2 Boys club forum)