If you go back on the SAM website and click on the link to the membership secretary Steve Rowe, you can then send him an email directly. He's normally good at getting back to people but he might be away on holiday or something, but he is dependable and should reply.
SAM Sundays at Sarisbury Green stop between November and March but club meetings continue throughout the year, as do ride outs, again it's all on the SAM website.
I don't attend many rides or meetings, but I did my "Skills for life" course with SAM and found it enjoyable and enlightening, well worth the course fees. I don't agree blindly with everything they teach, preferring to develop my own style but much of what they teach is excellent. The slow riding courses in particular are superb and always very well attended.
You won't regret it, how much you get from it is up to you.