Couple of other suggestions for getting round this problem:

1) Has anyone tried using a CE device with the IR interface to control the unit?

2) Or how about using the serial port on the back of the box?

3) And lastly: htttp://www.pacelink.co.uk sells units that allows channel control of Pace satellite receiver via the Scart port (albeit using a PC as the controller). Maybe something similar could be built for the cable box?