No need to test the diesel that I put in my car on saturday evening as the fuel supplier has admitted liability for suppling contaminated diesel. In my case, my car broke down about 1 mile from the service station and couldn't be re-started by the AA. The AA man checked the fuel, before attempting to re-start. He said it was definately diesel, but "a bit cloudy" and towed me home. The contaminant was water and the sample of the diesel I have from the VW garage is quite turbid , so I suspect there might also be some surfactant present. I think water contamination of diesel must be be rare, because I think the VW dealership didn't believe water contamination at first, but they do now after having to fix more cars that filled up at the same service station as me. Anyway, after flushing out the fuel system, the car appears to be OK, although I wonder if any damage has been done. At least the Fuel supplier admitted the contamination quickly, but it must have been pretty obvious.

It doesn't take that long to fit or remove once you have used it a few times. It is awkward for the first few weeks but you soon get used to it and it becomes automatic. I have one on each car. They also loosen up after a few months use so they become less awkward over time. Each one of mine is several years old and have been taken on and off several times a day at times so they are definitely durable and reliable.

I have a half cover from Halfords and that is much more awkward. The disklok is much better in terms of build quality and ease of use.

Vulcanising used to involve melting the rubber on tyre or patch making a seal that couldn't unstick. I've seen chaps sitting by the road in Africa with a tin of paraffin or something of the sort burning inside a removed outer cover, doing a vulcanised repair. Not really the sort of thing you'd want on your 911 or Audi RS6 I suppose, although it must be better in the context - rough roads, long distances - than a bit of glue.

Try APlan themselves (we do it by 'phone) rather than marmalade - we dealt with them for daughter and they were by far the best quote (about £700). They could not give us a good deal for our son though!
For our him we took out a multiple car policy with Admiral - one car in my name, one in his - took out his policy initially then agreed to add mine for the last three months of his policy Overall, for both cars, it worked out much cheaper - and that was after he had had an expensive prang. Suggest this to your neighbour as one way to go.

At a guess, because M4 connects up with M5, which M3 doesn't, and the SatNav would rather stick to motorways.
May depend on how priorities have been set in the SatNav.