Charterhouse http://www.charterhouse.org.uk/
Windsor Castle: http://www.royal.gov.uk/output/Page557.asp
Other Windsor activities:
FYI - Check out these event around Godalming
http://www.godalmingchoral.org.uk/gchoral.asp?p=3
http://www.godalmingchoral.org.uk/gchoral.asp?p=8
Alternatively, the Church in Dorking (just 15 miles away) is having a Vaughan Williams festival that weekend:
And the same festival has a closing Vaughan Williams "Songs of Praise" (Down Ampney et al) at 6:00 p.m. that night.
Intriguingly, there's a showing at 2:00 p.m. on Sunday of the Oscar-winning 1941 movie "49th Parallel" for which Vaughan Williams wrote the score. And as the title suggests, there's very much a Canadian element to the plot: