The best thing anyone can do is throw away the free router given to you by your ISP there cheap and tac. And buy your own I am with EE I set up there free router and the Wifi speed was capped to 54 Mbps where as my netgear nighthawk modem/router on 5ghz runs at 1733 mbps and the 2.5 ghz at 800 mbps so while i dont have that as a connection speed I do get my 300 mbps down speed over the wifi. Also the way the routers work the free ones create bottle necks on the network ones with multi core CPU and deal with data requests so you get no bottle necks. You dont need the lastest newest router but investigate what the differences are.
Just remember cheap no good, good no cheap.
If your thinking of buy a new router dont forget you might need a modem/router. or just use the free POS as a modem and attach a better router and use its WIFI. Also the wifi booster work well but they do need good wifi connection to start or a hard wire from the router. Again I use netgear for that and the link speed is the same as the main router and it has the same name so unless you login to either of the router or booster you have know idea which you connecting too.
Wife works from home
2 kids always online
and then theres me the biggest drain the the network we get no lag or drop out on either hard wire or WiFi
But to answer the main question
EE
300 MBPS Down
50 MBPS UP
Birmingham
£43 per month well worth it