Funny you recommended using a Unifi access point, that's exactly what I did. I returned the new router, and bought a much cheaper Unifi access point. Put the Vodfone router back, ran an ethernet cable from the Vodfone router to the other end of the house (luckily I have good underfloor and ceiling access). Placed the Unifi access point in the middle of the ceiling - you can do that because those devices support power over the ethernet cable. Much better coverage now and got some money back.