Hi Guys,
Just thought I would update and possibly help others with similar problems..
I purchased a 'guaranteed' air con control unit from a breaker in Germany for £35 and prepped myself for a weeks holiday to strip everything down. Just prior to starting on the Saturday I happened to find a solution offered that wasn't a 'fix' as such. The guy advised that he disconnected the electric preheat positive terminal and it resolved all his issues - sounded a bit far-fetched but thought it worth a try (If I'm honest I was looking for alternatives because the strip down was giving me nightmares!)
Anyway, cutting a long story short, I disconnected the positive cable and made it safe, tried the air con and amazingly everything now works!! All the vents open/close when they should, temperature control is back as well. All I have lost is the pre-heat on cold days (which I've never had in other cars) so not a loss really - win/win situation for me!
Oh, anyone need a s/h air con control unit I know where there is one!
Ian