Thank you to so many of you for addressing my concerns in a helpful and supportive way. I've been really interested to read about other people's experiences and I'm pleased that what I've said has resonated with many people so I don't feel quite so frustrated.
To give my thoughts on a couple of things that have been said; I am fully aware that some young people will no doubt be arrogant, although I personally haven't met many (and on a slightly unrelated note, in professional terms, the young performers we've had at our festival have generally tended to be much less arrogant than older ones).
I have not done the folk degree, and while I have objections the concept, I am much more a fan of an 'open door' approach to folk music rather than a closed one, so if they want to do it, fine. The fact is, it exists and we should be accepting of the people who do it.
I obviously did not go to all the sessions and singarounds mentioned and if I do go back, I'd give them a go and am grateful for the advice. I want to emphasise the fact that with the singarounds I did attend (well trained as I am by now in folk club etiquette), I turned up early, made myself known to the MC and put my name down in the proper way. At one, even stood next to the MC for the duration without success.
One thing that has been mentioned a few times bothers me, and that is that you need to go to Sidmouth a few times in order to 'build' on the experience. I find this a bit perplexing; why would you keep going back to a festival so that one day you might enjoy it? In my own festival organising experience, I would be incredibly concerned to hear that people were doing this at our festival.
One thing of particular value I think is worth echoing was Reynard's example of some older people being annoyed about young people singing Liege and Lief songs. I think it is important to emphasise the value of encouragement - the first song I ever sang at a folk club was A Sailor's Life, learnt from Liege and Lief. If people had been rude to me after the nerve it took to get up the first time, I would never have stuck around and learnt other brilliant, unusual songs from amazing collectors.
Thanks again everyone.