Sounds like a good plan. I just got a Pronto 'cause trying to learn the IR codes from the Pace remote caused my Cambridge Audio M1 (i.e. Remote Angel) to crash! Crushed that the Pronto has the same problem.
A new set-top box would seem to be the solution but how long will it take and how much will it cost? I haven't even got cable email yet so I'll have to remain sceptical over whether C&W will cooperate!