They changed the sensor yesterday so that's all done. I also added the 4l meths this morning and went on a 60 mile drive. All was going fine until about 30 miles in when multiple warning lights came up on the dashboard: lower washer fluid, brake circuit failure, battery charge fault, bulb failure, parking brake, ABS fault, and SRS fault (intermittently)!
I carried on driving home as everything seemed to working fine and the engine temperature wasn't rising, but the warning lights stay on now when I restart the ignition. The car drives as normal with no driveability issues.
I was wondering if this could point to the alternator problems that were mentioned by Dirty Rooster earlier?