Depends what you want from a club.
You can get 1/3 party CV cover by joing BC, LCC, Cycling UK etc .
However if you want to develop as a cyclist and to put something back into the sport then do join a club. Preferably one that holds events ,is genuinely inclusive, and which develops and supports it's members participation in cycle sport.
Rapha does seem a bit expensive. My clubs annual membership is £25.