Hi Krikor and Lefteris,
Thank you so much for taking the time to look at this.
I have found, much to my embarrassment, that it is not a K2 issue.
We found that the problem was weblinks. As the tag was to track clicks on external links, I had set the condition for the trigger to exclude links that contained catholicenquiry (so that internal linking isn't captured). As weblinks routs users through internal linking, the trigger wasn't firing as the URL it was being routed through contained catholicenquiry.
I have since changed the trigger to fire when the click URL contains weblinks and it now works like a dream.
Thanks and humble apologies again.
Rene