I have just noticed this event, and thought it might be interesting for the first time buyers in London to attend tomorrow:
There will be some Housing Associations present there as well, so you might be able to go and ask specific questions about the houses that interest you in particular.
Inspired Homes (the sales arm of Inspired Asset Management) will have a stand there, too. And will be presenting their new properties for sale. Some of them are listed on their website:
http://inspiredhomes.uk.com/