In message ,
David Paste writes

Can anyone recommend a make / model, or recommend a make / to to
absolutely avoid?

I am using a Fritzbox 7530 with Repeater (large, old house with solid
granite walls) and am very pleased with both. The 7530 has a USB socket
into which is plugged a 4TB external hard drive as NAS, allowing sharing
of films or whatever with the family, via wi-fi. No stuttering or lag.

See recent threads here which helped me set everything up, although as
you already have a similar setup, you probably won't need help.
--
Graeme