Regarding the currency:

If you start handing those notes over in pubs you will shortly be hearing the traditional phrase

"A b%^&y twenty, have ye nothing smaller?"

break a few up into fivers asap. :)

Also this is a good moment to have your trouser pockets re-inforced as we dont have a one pound note anymore and instead use slugs of milled copper which are destructive on thin cloth :)

Alas Maidenhead Folk meets on a Thursday but I believe Herga is on a Wednesday and Nettlebed on a Monday and both less than inch from London by OS map :D