Volunteers needed to fix a leaking roof for Lucas in London

I'm a school janitor living in London. During the last storm water started coming through the ceiling in 2 places, and the kids' bedroom is no longer usable. A roofer quoted $2,600, which isn't something I can pay. The good news: a local hardware store has donated the corrugated iron sheets and timber. What I don't have is people to do the work. I'm looking for three or four volunteers who can help over a weekend. Experience helps, but it isn't essential - I'll have a licensed roofer supervising for safety. All you need is sturdy shoes, gloves and a willingness to work. I'll provide lunch, water and lots of thanks. The work will be done on the ground and roof with proper harnesses. If you can only help for a few hours, that's welcome too. I hope life is good to you.