Not at all - as long as the vehicles are not causing an environmental health problem, which I doubt very much.
The vehicles don't need to be taxed if they are kept on private land and never go on the public highway, although they must have a SORN.
Your only possible redress is if he is using the premises for business purposes which require permission from the council; or if there is any covenant on the title to the property relating to parking of vehicles on the driveway - highly unlikely.