Ray
I have done this and re-enabled procmail for all of the users prior to sending my last post. I have had someone help me and we've solved the problem. I'm unsure as to why this solved our problem but it did. Firstly we removed spamassassin completely and also removed clam antivirus, downloaded new scripts from swerts knudsen and installed clam av - updated, installed spam assassin and updated.
And now Spamassassin is working correctly.
I suspect that an outdated engine for clam antivirus MIGHT have been causing the issue with procmail not deleting messages as it should have, but removal and reinstallaion of BOTH of these solved the spamassassin issue for me.