Yep, the 26th is Wednesday, but that's the night that Bedford runs:

Dr Faustus at The Gordon Arms, Castle Road, Bedford 01243 296519

Not much good though if YY's seminar continues in London the next day though...

How about Faversham? Simple to get back and there are three St Christopher's Backpackers in Borough High Street, London Bridge. Email: bookings@st-christophers.co.uk. Phone: 020 7407 1856.

As Kevin says, there's really nothing happening within the M25 that I know of on Wednesdays.