There's an Old-Time Festival in Gainsborough, Lincolnshire, in February each year. Not quite the same thing as Bluegrass I know, but a nice friendly 'do' over a weekend, with very good attendance and lots of good guest artists. Plenty of opportunity to jam too. Might be worth a look. I bet there'll be a thread about it on here a bit nearer the time, or my name's not SJ Mooseplaster!
SJ :0)