So I changed it for a 2nd hand one which turns over much slower & has occaisionally clicked. I s there a relay between the keyswitch and starter solenoid? Where is it ? what No? I tried the removed one on the bench & solenoid seems fine!!!

I've never touched a diesel omega, but after having the same problem on my dads transit, and trying lots of things including new starter and dual mass fly wheel that had eaten itself, my dad assured me the battery was a good un.

Problem still there and it was a duff battery after all! Don't want to state the obvious or insult you but is your battery ok? The transit had exactly the same symptoms.

Sounds like a bad earth

Need to check battery and charging condition as well as lead connections and earthing. What can throw a red herring on the 2.5TD's battery system, is a sticky glow plug relay, it competes with the charging circuit if stuck on and and kill a a fully charged battery within minuets even with the ignition off and key out. tends to be an intermittent thing as well.

Chris