If the Courts cannot prove your son lives with you, such as him receiving Benefitsor mail based at your address, then there is nothing they can to. Ignore advice given on watching your home. No one is going to 'watch your house' , how ridiculous is that? for a couple of hundred pounds worth of fines? He will be given a choice to pay off his fines weekly which he must take, even if he doesn't do it, that, with no evidence of his 'abode' at your home, will ensure you are not involved should there be a recovery process.