"
.....often specialised sessions especially at the bigger festivals like Whitby, and may be described loosely as 'beginners', 'intermediate', 'experienced'. However they are not always advertised as this, but looking at who is down to run the session is often a good indicator. "

Well, that is all very well. But people who don't know the person running the session won't know what to expect.
Same applies to other things on the programme
e.g. At an Irish Ceili with Jerry O'Reilly the dancing will be Set Dance for those who know the dances - no walk through, probably not even a call. And lots of song in-between.(not sure if there is one this year)
So you can waste a lot of time going to the wrong thing. And leaving the person running the workshop with the difficulty of whether to please those who did know or see who turns up.

Yes you can sometimes get a clue by cross-referencing the item in the programme with the biog in the 'other half', but not always.