Ralph.
There ARE two seat gliders with side-by-side seating but not in general training use. The venerable T21, Sedbergh comes immediately to mind and a surprising number are still around. Most will be privately owned but some will be part of the club fleet. We have one here at Oxford. There are modern side-by-side two seaters but I`m not familiar with them and they are not common, not in the U.K. anyway.
If yo can hear at all, I would imagine that radio is no big problem. A good headset with a volume control should suffice. If I turn mine up to maximum it is almost unbearable.
Mike W