I have had free cavity wall insulation done, no catches.
There used to be a scheme that anyone could have it done, however properties with less than a 50mm wide cavity and houses on 3 storeys were designated 'hard to treat' and the companies refused to do them. Now they have invented different methods and products and 'hard to treat' properties can still be done so that you have the same opportunity as those people with properties that are not hard to treat.
Mine was done with a type of expanding foam, it was the first house to be done in the North West of England and I had 3 teams installing it and about 20 blokes turn up to watch. It was a right circus.
No adverts, the company is based in Dukinfield.
They also do solar PV but I don't know about this car charging lark.