My company credit card has my name on it and its agreed with the card issuing company that i can use.
But if i used a card which was say issued to you even with your permisson it may not be illegal but it would be against the terms and conditions of the majority of cards I have seen it appears if the card issuing company which to uphold for some reason.
If you were to get an additional card for a person and its registered in their name there should be no problems although they may only issue to UK residents.
Again whether criminal law is broken is one thing but breaking terms and conditions of an agreement you sign with the card issuing company may leave u in a spot of bother in certain situations.
Also the companies may ask if payments keep being made abroad to check with you for security reasons.
Again many people get away with things but doesn't mean if the card issuing company want to they cant say you have broken the agreement if it suits them or comes to their attention..
Again would you write to your Bank and declare your son has been using your cheque book for the last 24 years? If he has been using your signature then i would think that was fraud surely?