YABU, massively so.
I am a councillor, an amongst other ludicrously outdated an divisive traditions, this is an issue that I have been offended by.
A councillor is expected to attend meetings. Figures on attendance are published. When a councillor normally absents themselves during a meeting, it is for a very important reason, ie. they have a prejudicial interest in a matter in hand an therefore should not be present. You can't just walk out for a little while when you feel like it. Press and public are there.
Is it appropriate to spend precious time (and public money) worshiping, when many members will not be believers, or may even be offended?
Many of the arguments on BBC etc. website against this ruling is that an atheist could just sit an think. At ours, all must stand, as decreed by the chair. Some (myself included) stand and look around the room, but I know that many obediently close their eyes and whisper 'amen' simply because they don't want to be criticised by their political leader.
It is divisive. Not a wide enough variety of people stand for election. Christian prayers give the impression that only Christians are welcome to stand for election. Granted, most people are not offended by prayer, but some are. As it is not possible to sit the prayers out, I do believe that some of these people will be put off standing for election.
In my town, you see the same old boys network everywhere. The Masons are town councillors, district councillors and county councillors. Most are also members of the local Conservative Club. We need variety, not incest.