Thank you for all the replies.
Paul: Unfortunately, I don't have a photo of the poster or printer details. Sorry, I wish I did. I saw the poster in person butI didn't take one. There is no online pic either sadly.
Jeff: The pic you posted is the same as the one I saw in terms of the main details - eg the tag line is lower down than in the original release quad and it is made up of blue lettering (the original release tag line was in a more greenish coloured font). So in broad appearance it looked like the rerelease version of the poster, but the dealer said it was a second printing from the first release (his logic was the film had proved such a surprise hit at the UK box office, they had to do a new print run).
Hicks77: As Bruce and Paul mentioned, both images from Posteritati's site look like the original release version. The poster I saw was the same as the rerelease version as Jeff posted but the dealer claimed it was from the first UK release and was merely a reprinting, hence the change in text placement and colour.
I find it odd that for a second print run they would have changed the tag line positioning and font colour. To me, it makes more sense they would do this for a rerelease years later, to distinguish the two. But I could be wrong to think this. Thanks again for any advice.