I think this problem might have solved now!
Apparently, the fault was likely due to the fact that I had commented out large sections of original template files that I was redesigning…
This was because it is my first venture into PHP based pages and working with templates in this way, so I was trying to work out what parts of the code did what and whether I would require them for the new style pages I was working on. I commented out large sections so if I needed something adding back into the page I could easily find it and make it display again, which I thought was a fairly sensible way of doing things!!
Anyway, the good people at Adepteo who host our site have said that IE couldn’t handle the large amounts of commented out code and the pages I have checked so far seem to be displaying as well as I could have hoped.
So, if anyone ever gets a similar problem… try that for a solution.