That sounds kind of strange ? SWR meters don't do anymore then tell a guy weather or not he has a good or bad match ,certainly doesn't add power or anything like that, it surely wouldn't make any sence for them to be illegal in line with the radio and antenna( personally wouldn't want one in line if all I was running was a radio in the first place ,I would think there was some kind of slight lose there) ....throw a amp in line there after then I would guess to say you were illegal ? ..So many radios themselves have built in SWR meters to begin with ,I would hate to think they were illegal as well ? ....I really have know idea what the laws are in the UK ? but I must admit ...that does sound a little strange to say the least. Good Luck