colinr - what version of ZC are you using? Your html_output doesn't match the 1.3.6 one...and there are two sections at about line 120 and about line 196 with similar code to above...neither of which is anywhere near the end of the file!

However, the second instance does have some effect, but not what I was hoping for! The main product image has disappeared and the attribute images now appear to be expanded thumbnails!!

OK, I'm going to start this again.