There are no 'Submarine clubs' as such.
There are model submarine organisations, which provide newsletters/magazines, meet up at shows, and there are the Dive-in's that Richard mentioned.
I represent the Sub Committee here in the UK, and we have about thirty British members dotted around the country, although the Sub Committtee has about 6-700 members worldwide. Some of these guys are also members of the AMS, which has about 45-50 members I believe.
Sub Committee-
http://www.subcommittee.comAMS-
http://www.modelsubmarines.orgYou would be very welcome at one of the Dive-in's, the first of which is on 4th October. Completely free, and the best water to sail a submarine in that I have encountered. More details here-
http://s181686668.onlinehome.us/phpBB2/viewtopic.php5?t=9056You may also like to check out Norwich model boat club. A very enthusiastic following of model submarines there, with a super pond, it's a bit of a drive from Colchester, but a straight run.
http://www.nmbc.fsnet.co.uk/Andy