[Chris]

There are a couple of potential problems with that. First, you're taking a chance that the RF-output frequencies of the Freesat and Sky+ boxes are sufficiently different to avoid them interfering with each other. I don't know how you would determine those frequencies without actually having both boxes already and tuning into them. If they were clashing, you might be able to change one of them in the way many VCRs had to be adjusted when Channel 5 was launched, however I don't know how easy it is to do that. On old VCRs it was a tiny rotating knob you could get at with a screwdriver.

The other potential problem from a distribution point of view is what happens when you try to use the FM input socket for one of the boxes. I have a sneaking suspicion that this actually won't be an issue - I'm not sure that there's anything clever in the splitter to ensure only VHF frequencies can pass through that socket. But I don't know. There are some RF experts on this forum however, so I'll leave one of them to confirm this.

Your major problem, of course, is that even if you only want to have one Freesat box, you still need to feed that box from the LNB on your dish. You would need three cables; one for Freesat and two for Sky+. You would need to replace the dual-LNB currently installed on your dish with a quad-LNB and add another cable.