I think Pace is the company that made a cable tuner that used IrDa. Most learning remotes can't learn IrDa, even though many could send it if programmed some other way.

The only Sky+ I know of uses an RC6 variant, which is very much easier for a learning remote than IrDa and shouldn't be any problem for a Pronto.

I forget which company(s) make the box for SKY+, but I think there is more than one company and Pace is one of them (and the SKY+ IR signals are the same even if the brand is different).

So if all my vague memories on the subject are right, Pace makes both an IrDa system that would be hard to learn and a SKY+ system that wouldn't be hard to learn.