Hi,
Not sure if this is a UK region issue but on my 5Ghz settings the only channels I get are 36,40,44,48 I can't find anything that states how many should be available.
Basically at the moment I am on 5GHz N only WPA/WPA2 Personal Channel 48, I have also tried 44 and it is the same. Its strange how both bands are affected though, these page timeouts happen on the iPad 2 which is connected via 2.4Ghz, the rest are on the 5Ghz band.
Both Xbox One and PS4 are wired into a switch and then into the router, I am thinking that I may have to test another 880L as at the moment I do not have anything else available to test.