Cheers Moggy, the problem is sorted. Luckily its not the door pins etc. It harks back to when some theiving b*****d smashed the drivers window to nick a pair of sunglasses. We had mobile glass company out to replace it and he didn't get the door trim on correctly. Since then everytime we shut the door it pulled the trim off ever so slightly to the point where the bottom of the trim now gets hooked over the door threshold, making the door stick. I've banged the trim back on and all is OK again.
What is really annoying about all of this is that when the thief smashed the window, he didn't have to - the car was unlocked with no alarm on. He could've had the sunglasses by just opening the door!!
Thanks anyway for your suggestions.