hi, teryc!
Ask at LASHAM gliding society for advice, the fellow who ran the cafe was about same height as yourself. He arranged blocks on his shoes, or they were installed on the pedals, not sure which, but at Lasham somebody will remember!
You can only adjust back padding to a degree that doesn't cause your body to interfere with the stick! As far as back padding goes, may I recommend that you make a square cushion out of a stack of NEWSPAPERS, held together with package sealing tape, that brown sticky kind, and sew on a nice fabric cover.
I make lots of these for the gliding club at Shenington, a lot of people use them and so do I. The newspaper stack is NON COMPRESSIBLE. Which is the important thing to have behind your back, rather than squishy cushions, which have actually figured in a very nasty accident, and I when didn't know better, also had an interesting flight when the squishy back cushion compressed, and I ended up departing the controls, sliding rearwards on a winch launch.
Gliding clubs....Tibenham, right? Norfolk Gliding Club on the internet. They have a K13 training glider, and couple of K21 gliders. I recommend you learn in the K13, it is easier to make adjustments in the front of the 13 for smaller pilots, and also it is useful for stall and spin training, so it does everything, and is yet docile. Beloved by us at Shenington, and also the workhorse at Lasham....have a go in a K13!
When you go solo and start thinking about a share in a glider, its not too early to ask people with K6 gliders, or even a K8, to let you sit in it and find out which you prefer.
Quite true that very tall people have problems. I sent one guy solo who was 6 feet 7 inches, but he had to take off his shoes, and leave the parachute behind. (and that brings up a whole new delicate problem! should the instructor go without a chute as well? or if departure seems vital, leave the student behind? let him hang on to my chute? yikes! It seemed good manners not to wear a chute either, newspaper cushion fit the gap behind my back. Fortunately he was a very very quick learner, and I sent him solo after only 23 aertows.
But anyone can fit in the open cockpit T21!
We do have gliders (the K13 again,) fitted with hand controls for paraplegic pilots, but if your legs work, best to learn to use the rudders with feet if at all possible.