Unfortunately you just missed the London ALT.NET Conference. But there is still an active ALT.NET group in London.
The ALT.NET UK group is a great group of talented and dedicated individuals doing some awesome things including some of the things you mentioned. I highly recommend you get in touch with them and maybe attend one of their recurring events (ALT.NET London Beer Night, etc).
Here's their home page:
http://www.altnetuk.com/
Here's their mailing list:
http://newsriver.altnetuk.com/
Here's a combined blog feed of ALT.NET UK-related stuff:
http://newsriver.altnetuk.com/
Here's the wiki from the conference they just had:
http://www.altnetpedia.com/London%20Alt.Net.UK%202nd%20Feb%202008.ashx