I got a reply from an autoelec on another forum.
I'm posting his reply here so it can help anyone else with a similar problem

"The clicking was the warning light relay part of the regulator, which is switched by the alternator star point. The 2.2 amps draw is the alternator field circuit winding current draw.
The problem is that one or more of the positive diodes are faulty and allowing leakage to the star point ( 7 volts normally) which switches the regulator. If you leave it happening it will also burn out the warning light relay coil in the regulator and cost you both an alternator and regulator, if it hasn't done that already.
Forget the isolator, relays etc and fix it now.
Cheers.'