I'm not sure NICE should necessarily have an agenda. However, there is a strong and influential CBT/GET-type lobby in the UK who earn a living, etc. from these treatments. Also, unfortunately I'm not sure there are many competing treatments at the moment that have the sort of evidence (at least two positive RCTs) NICE are looking for.
What is the second positive RCT that you are referring to, Dolphin? (Assuming that PACE is the first.)