A friend of mine from the US has a lengthy stop-over at Heathrow the evening of Saturday, 30 April and leaving the next morning -- May 1st. I'm planning to head to London (by train) to get together with her. She's a folkie too, and I think she'd enjoy a proper English May Day celebration with Morris Dancers, etc. The tricky bit is, she'll have to be back at Heathrow by 10 am, so it would need to be one of those crack-of-sparrow-fart sunrise type celebrations.

Anyone know of any? If so, how gettable-to would they be using public transport? Is there anything easily accessible for someone taking the tube?

Many thanks!