The issue with this router is that it is a rebranded sky Q hub which uses the multiroom Q boxes to amplify the signal and therefore was never intended to be as powerful as routers from other providers.
Nowtv doesn't have the Multiroom Q boxes as Sky does to amplify the signal and so will it always be a sticking point.
Hi. Just moved to Nowtv from BT. Had a straight forward change over. My desktop has 65.2mbs download with 18/20mbs upload and the wifi has no problem through 4 block walls and into my workshop about 15 metres away.