So, for anyone who has the same problem this may help.
Saw the old aerial off just where there is a dimpled bit on the aerial stem.
The aerial stem below this dimple is filled with brass.
Get and old stainless whip aerial and drill a hole slightly smaller then the whip down into the brass.
Make sure this is very tight fit on the whip and then holding the whip in a vice or mole grip push/screw the cast aerial base onto the whip.
Job done. Works a treat and won't bend as easily as the standard aerial.
