I think I know what the fault is on this...I had the same thing on my Toledo TDi.
Its the brake sensor on the brake pedal!!
The fault I got on mine was the glow plug light was on (wont affect you
) and I had no rear brake lights at all. That was dangerous, but the thing that threw me was that I had no cruise control either, so I had two unrelated symptoms that I could see.
Try taking off the lower panel near the brake pedal and playing around with the switch, its a common fault and one that can be remedied by replacing the switch with a later version.
Its a weird switch, if you take it off and have a play with it you will see that it ratchets out, this extra extension is taken up when you press the brake the first time. Instead of replacing it you could try turning it a few mm either way to clear the fault.
HTH, I see you are selling your motor on P'heads. I've got a V5 Golf 170 now, but I don't think the Golf is worth the extra money over the Seat TBH. Think I may be in the market for one in the near future.