Don't want to be controversial as the WABAM group are great, but just think it's worth pointing out that there is a local Rospa group too which is quite active.
The main difference is that Rospa have a mandatory re-test every 3 years for no extra charge - you may of course see that as an advantage or a disadvantage. For completeness I should mention the IAM do a re-assesment for £35.

If you are thinking of doing a course then check out which group might be best for you.
If for example you go to church on Sunday's you might find one group suits you better if they do rides on Saturdays. Similarly if you are interested in car training as well, you may find one group suits you better.
For every person that says I have a great experience at X and Y were unfriendly - you'll find someone who says the exact opposite.
So check out the websites and the activities. Both groups should welcome prospective members.
I think it's fantastic that there is a choice and would encourage anyone to do more training whether it's IAM/ROSPA, california superbike school, able training or whatever.
It's all too easy to do nothing.

Most people find that their enjoyment of their riding improves and not just their riding standard and their safety.