I want to thank everyone here that helped with this last night (and the guys who pm'd too), I am pleased to say that it's now sorted.

I recon that when I originally ran the scanpst program I didn't find all the pst files and because of this the operation took only a few mins and found no errors but once I knew where they all were (then desktop) I scanned again and it took well over an hour and did find problems. I then pressed 'repair' and after that I inported everything back into outlook and all is now good It did take me until 2.15am though!!

I still have no clue what caused the issue.

Thanks again