After much research and resetting network names, keys and a miriad of other things, I eventually called Sky.
Sky have this as a known issue. The Sqy Q actually works as it should but reports that there is no internet available! (Go figure ***). When I tried to download it actually works even though it says there is no connection.
Sky went on to sya that the Sky Q and BT Whole Home discs are not communicating as they should.
I got Whole Home the other day & got everything connected OK apart from my SkyQ Silver box. Whether I do WPS or select the SSID and enter the Key, it connects OK then a minute later drop the connection (reason 8 according to the log). Tried different channels, and Compatability Mode but nothing works. Spoke to the helpdesk this morning & BT know it's an issue, not sure whether Sky will fix or they'll make a firmware update...