Under the boot floor, see attached photo, area circled in yellow. Pull out the multiplug with the purple cable. In the photo, the plug is already pulled and taped to the grey plug/green&black cable to prevent the disconnected plug from rattling about. The socket is taped off with blue insulating tape. This disables stop/start. Be aware this will show a stop/start fault code if you ever attach an OBD reader.
My only ‘gripe’ is that I think either the last owner or Volvo has put a set of Falken tyres on the rear, they are brand new, it has PZeros on the front.
Matched pairs of tyres on the same axle are fine, it’s where you have mis-matched tyres across the axles where grip/braking can be problematic
A lot of people put the Michelin PS4S or Continental Sport Contact 7’s on as they tend to work a lot better in this country. I’ve currently got P-Zero (grips) on and when the temperature is sub-optimal ie. below 23°C they don’t inspire confidence at all. I still have about 6mm of tread remaining all round so can’t justify replacing them yet