Al and I were up at the Bradfield Weekend last year, and helped to host a session at the Royal at Dungworth on the Saturday lunchtime. A number of the "folkies" there joined in with gusto with some tunes from the 30s and 40s and clearly enjoyed the contrast with the mainly traditional content of the weekend.

As Al has said above, it's free and is part of the street festival - no charge - come or stay away as you please. As for folk festivals being nothing but folk, a quick look at, say, the recent Cambridge Folk Festival should disabuse you of that. As for Alexei Sayle and his opinion on jazz, who gives a toss.