My understanding is that you cannot be carried as a passenger in a car if your duty time is up, and VOSA once gave me a friendly warning because my weekend break started at Aylesford and I started on work Monday from Sittingbourne, with 30km of missing mileage.
They asked why, so I explained that I had dropped the truck off at Volvo for a service, and my boss collected it on the Saturday and drove it back to the yard.
They then asked how I had got from Aylesford back to the yard on Friday, and I explained that my boss’s brother had collected me in his car.
They told me that this is classed as other work, and I should have made a manual entry covering it on the back of the tacho card.
I didn’t get nicked, presumably because I passed the “attitude test”.
I believe there was a test case involving a coach company confirming the same thing.