Thanks for the reply, the clicking sound is only there when the engine is cranking. If I turn the ignition on I get the usual clicks but then when I turn the key to crank the engine I can hear a relay or something clicking as though it's latching and then releasing constantly.

I've checked the feed to the solenoid on te starter and it does get 12v when you turn the key but this problem seems to be intermittent so may of just been working when I tried it. Do you know where the 12v feed to the solenoid comes from? is it direct from the ignition barrell or does it come from a relay somewhere?