Right, going to say meet at 12 to make it easy for everyone to get there for the same sort of time. Best place to meet is a small car park between Fassnidge Park and Rockingham Recreation Ground.
1st Uxbridge Scouts Hall, Rockingham Recreation Ground
Rockingham Road
Uxbridge, Middlesex UB8 2UW
If you put that in google maps you will get the exact location (the post code gets you to the other end of the road so its fairly close)