I'm a member of the 'North Essex Photographic Workshop'. (
website)
We meet every Tuesday night in Clacton (or at a prearranged local venue for field work).
The social aspect is indeed pleasant and the practical exercises are also very useful. (The planed program is on the website)
I've heard that some clubs are very competitive, and members in these can hoard their knowledge to make sure they don't give secrets away - The workshop is very much the opposite where we all try to learn from each other.
Membership also gives the opportunity to exhibit your work without the difficulty of arranging the whole exhibition yourself.
I'm very glad I joined, and with the cost less than a pint a week it's one of the cheaper elements of my Photography!