hmm... apparently seatcupra isn't too fond of other forums... i b i z a o c
 
worked a treat

Having read all the comments on this thread I decided to go out to the ariel I've been having a go at (for about three weeks) and unscrew it all the way...Then pinch the base with large mole grips and give it a progressive pull. Came straight off with little effort at all and no damage to the roof or antenna mount. :)