[Cookeh]

Battery clips are £4 something from Volvo.

Audio wise, the 11 speaker Dynaudio package is vastly superior to the Dolby's.

Electric seats are pretty difficult to refit but don't have any issues with reliability. You can bodge the refit easily, though if you're OK with that. Plenty guides available on Matthews Volvo Site.

Cruise control is incredibly difficult to retrofit, requiring a lot more than just a relay and a set of pedals. I really wouldn't bother, will cost a significant amount of money and involve the dash coming out, pedal box coming out and a lot of fiddly wiring in the engine bay.