I'm pleased that your phone call to 101 produced a good result because there are too many motorists on the road that don't abide by the rules and honest motorists have to subsidize those cheats.
My own dealings with the 101 service were not a very good experience
The first time I reported someone for driving with a MOT that had expired was because they were texting at the same time and driving in the middle of the road with a car following it. The operator said that unless I had a photo of the driver texting there was nothing they could do as I had no evidence. So I replied by saying that you have the evidence on the DVLA data base so what as you going to do about the expired MOT.
The operator consulted her supervisor and came back and said " unless the MOT is three months or more out of date then we are not interested" Unbelievable!
The second time I phoned 101 I reported three vehicles that had no tax, one of which has no tax, MOT or insurance and belonged to the same person. She asked me where the cars are parked and I said in the person's garden and the answer I got was that " the Police have no powers to do anything when the cars are parked in someone's garden" ( no SORN on any of the vehicles "
What can one do in the circumstances, we know that the DVLA is useless and the Police can't or won't act so the fraud is allowed to continue