I was a member in the 70s/80s and into the 90s, at which point I felt it was drifting away from the original concept and packed in.
That's the official website and to be honest, if you want to join a traditional marque club then that's probably the best one in the UK. (Lotus Drivers Club is the other main one, I was in both)
In the early days they did have alternative parts lists and in the pre internet days the quarterly magazine was a lifeline for articles, parts, etc. It was founded by Graham Arnold, PR/Sales for Lotus in the 60s and he was very good at the job, organising weekends away with ex-factory speakers who would give seminars on the cars. Again, pre-internet this was brilliant.
They would advertise specialists, sold regalia and some books, but never parts. Unlike some clubs (MG/TR) I don't recall them ever setting up to reproduce obsolete parts but perhaps they have since I dropped out, I don't know.
Brian