Just cut the loom and find the positive and negative and attach it to any switched 12v supply like the ignition switch and ground the negative to the chassis. pretty simple really. Not sure about the heated side of things but to get the things moving any 12v supply will do.
The heated seats put a significant electrical load on the car. Make sure you do this right!
1. If in doubt draw power directly from the battery +ve pole via a correctly rated cable put a correclty rated fuse in series here (nut sure but say 30A as an example)
2. Pass this to two separate relays that can only be engaged when the ignition is on and the relevant heater switch it pressed
3. Feed each seat from the relay and put another fuse in series to each seat (15A) each
4. Secure each connection and insulate correctly.
Reading the instructions (although not 100% clear), it seems that you connect one wire to the battery, another to a switched connection (e.g. 12v socket?), and the final one to ground. The kit comes complete with a harness and relay (so I ***ume the relevent wires are fused)?
Thanks Jayok. Yes doesn't seem to be a massive power consumption. Would be a different matter I guess if I was doing both front seats. If I go ahead and do this I'll try and put together a DIY guide. Have to see how easy it is to get the pads between the sponge and seat cover without having to dismantle the whole seat!