I'm currently restoring a MK1 Interceptor, which has the same rear wheel set up. If the spindle is just clicking on each turn, the thread on the spindle or stub axle into which it screws is knackered. The arrangement is more or less the same as a Norton. The best way to remove the spindle would be by welding a bolt, say 3/8" UNF or similar, onto the hex end, & screwing on a slide hammer. Then just start unscrewing the spindle whilst operating the slide hammer.
Hope this helps.