The main Lotus club on our side of the pond is Lotus Ltd. They hold a Lotus Owner's Gathering (LOG) every year, usually near a track or other feature where your Lotus can stretch her legs as well as some other interesting attractions. There is a speaker with some connection to Lotus, banquets, a "casual concours", and sometimes a serious concours, a panoramic picture of all the Loti in attendance, and a lot of other fun with people of a similar affliction.
This one is in Cincinnati. They will announce the location of the next LOG there. If you can go, you should!