The unconference will run alongside all the main sessions, with exception of the keynotes, panel sessions and closing address. It will offer 15 or 20 minute slots where any attendee of the conference is free to give a talk or workshop on any subject of their choice (that would be of interest to a PHP user). If I've done my math correctly, that works out to about 12 talks per day, or 24 total opportunities for you to share your knowledge with others. If you've never given a talk before, this is a great way to get started! It's low pressure, informal, and intimate. What are you waiting for?
There will be a big sign up sheet at the venue itself, so grab a pen and write in your slot when you get there. I will be there as well, to help you and to keep things rolling along smoothly. Don't hesitate to seek me out if you have any questions at all.
The fine folks at PHPUK have also suggested that if you have ideas for topics before the conference starts, you can add them to the comments section of the Unconference page of the site.
See you in London!