My thanks to surfster supremo Desire Athow at NetCommuniities HQ for pointing in the direction of http://developer.yahoo.net/hackday, where a UK team are preparing for a London version of Hack Day at Ally Pally during the weekend of June 16/17th.
Details of the event, which is being quietly publicised in all the right places, can be found at hackday.org.
According to the organisers, attendees can expect the UK event to be similar to the Sunnyvale, California, event of last September, which my US friends tell me was similar to what the old 2600 Hackfest meets were like in the 1980s and early 1990s.
Ah, nostalgia -Ed
Anyway - you can register your interest via the Web site, which looks as though it's been encrypted to stop any Web spiders indexing the page(s).
If you drag your mouse over the encrypted text, it appears in decrypted format - neat!...