Hi Dave, I think that you're about as confused as I am about this. It was reported on some spotter's groups as being an 'equipment incompatibility' issue as to why they didn't go to Manchester to start with and it was then reported that some new EU regulations meant that they had to re-route to avoid certain countries.
We'll probably never know the real reason why they were held in Iceland for 3 days in reasonably good weather with 2 serviceable aircraft.