If these are penalty charge notices they are a civil matter and there is no question of arrest or of any involvement of police. (Does he remember what Court he was summoned to? If it was the County Court then it was a civil matter; if the Magistrates Court it was criminal.)
If they are Magistrates Court fines or fixed penalty notices issued by police it is a different matter. If that is the case, the most sensible thing would be for him to pay them off before coming back to UK. Otherwise, if he doesn't want to try & find out if an arrest warrant has been issued, he will just have to turn up and hope.