I have one and they do work providing you get the smart splitter. Go to
www.satellitecentre.co.uk and put "priority switch" in their search box. They cost £15.00 + £3.50 delivery and they get there within a couple of days (and no, I don't work for them !).
---------- Post added at 18:28 ---------- Previous post was at 18:05 ----------
Just checked the search on the Satellite Centre home page and, for some reason, you need to do it twice but the second search gets you there.