Thanks guys!!
I found 2 clubs listed on the MYA website, not too far away (Southwater & Hove). In fact the Southwater club are taking part in a wetland trust weekend @ Arundel this weekend, so I might just go over there & have a chat.
I also found a club, not on the site, but in Chichester, which is a bit closer...
DickyD, I actually went along to the boat show on the lake in Littlehampton the other weekend.. and saw a great 7 foot model of HMS Illustrious there! Sadly the weather put a bit of a dampener on it, and about 95% of it was powerboats, but it was interesting nonetheless. I did speak to one of the chaps there about using that particular pond... but apparently there are some politics involved, because it is normally used for pedalo's, so there's an argument over the usage, or something.
Thanks again guys!