Like you we were on a Just Park driveway. Ours was a mile or so from the ground so we weren't back to the car until about 22:15.
I thought it was curious that Waze didn't take us back to the M25, directing us over Hammersmith Bridge, picking up the A3 at Kingston and then the A243/A24 back to Worthing. It meant the first few miles were relatively slow going but we were back in Worthing before midnight.
Similar timing....but satnav directed me via Heathrow. Would have been home by 11.30 but roadworks on M25 around J10-9 caused a 30 min delay (3 of 4 lanes closed), and then the M23 junction was closed so had to go to J6 and back again.........suspect being further West yours picked your route as a quicker journey. Clever stuff.