Alternative Router

[#1]

Hi,
A family member of mine is considering moving over to fibre broadband. He is considering Plusnet. Because his property is rather spread out we are assuming he needs an upgraded modem/router. His existing BT Hub 3 struggles to reach all the rooms in his house. He also needs it to be VOIP compatible. I understand the new Plusnet router is not.
Is there a list of Plusnet "authorised" modem/routers?
Do Plusnet supply alternative routers?
Can anybody recommend a good router that is better suited to a larger property? I know there used to be an ASUS model that was quite highly regarded.
Grateful for any advice

[#2]

I use a Billion Bipac 7800N, somewhat long in the tooth now but has always given a good wifi signal (and has given 5 or 6 years service with complete reliability). I would imaging the newer Billion models would be as good, and I believe some of them don't need the BT fibre modem.

[#3]

VOIP compatible meaning what? The HH3/4/5 are all NOT voip routers. Most if not all modern routers will allow voip clients or hardware to work, but rarely have voip built in.
How much do they want to spend?
A hh5 would be a good bet to replace the 3.