Knowing the club you mean and the way some people treat you within that club I am suprised it has taken this long for you to decide this.
The reason I joind the club was the way you welcomed and helped me as a complete MTB noob. The reason I left was the way a certain core of the club behaved.
I believe the day that sealed it for me was a club run where we took a shortcut through church grounds and the grounds keeper came out to chase us. He was a pretty old guy and pretty red in the face, and clearly pissed off that the club route went through his churchyard. There was no reason for the route to go that way as there was other ways to go. This could have been solved by going a different way and leaving him in peace, or by stopping and chatting to him, ask where he would prefer us to go and generally making a new friend. Not by the two most "offical" and "senior" members shouting "Land Reform Act" in his face and cycling off. No need at all for that and it sums up thier attitude really.
I have no intention of rejoining this club myself.
However not all the people in this club are bad! I have made a few good friends through it (I would be honoured to call your good self and Bazz / Jo mates!) that I ride with outside the club now. I have also met a few poeple out and about where the club runs that are always happy to have people join them and ride with them. They just have similar experiences of the club that you have now had and want nothing more to do with it so wont post on thier forum.
So you dont need to ride alone, phone your mates and ride with them! Come ride with us (Pedro, Iain, Stuart, Barton on some very rare days) on a Saturday, I can pick you up on the way by with the car if I am riding that day. If you dont fancy that I ride Meikle Bin / CV normally twice a month so can meet up there anytime your free and fancy a ride at a slower pace than normal!
But once you free yourself of the obligation to ride with people you dont like you will enjoy the biking a lot more... I think it might be time for you to be a bit more selfish - you do a lot more for the club than it does for you!
Also there is something nice about riding alone, gives you time to think, means you can go at your pace (watch this tho as my pace gets slower and slower if I let it!), go that way to see whats there, push back up to do it again, or if your just not in the right place cut the ride short. Just make sure your good lady knows where you are and when your due back!