We bought a kid's universal remote from Argos, with big colourful buttons, then I put together an Arduino-based gizmo which received button presses from the new remote, and played macros of button presses to the TV and set top box. It worked up to a point, but of course it's defeated by any buttons whose meanings are affected by state - the button which toggled between the TV's internal tuner and the AV input was a particular problem.