I think you are confusing what equipment you need.
BT Retail provide a Home Hub3 which is a router that handles both wireless and wired connections. A hub is a different piece of equipment which gives more ethernet connections and are really outdated as ethernet switches are faster and only a few pounds more.
THe HH3 has 4 ethernet ports, only one of which is a fast gigabit port and the wireless connections give some people problems. You can safely replace the Home Hub with a cable router of which there are loads including the Netgear N900, choose one with the services you need the N900 has dual band wireless which is nice if you need it but not cheap. The router cannot increase the speed of the connection but look for gigabit ports as 100mbps ports are nearing their limit with Infinity.
BT Openreach provide a modem which handles the connection to the cabinet and sets the overall speed. Netgear do not offer a combined modem router for VDSL connections like Infinity and you are best not changing the modem unless you know what you are doing.
So u must plug the switch in the gigabit socket and the modem in the 100mb socket.
I might just get a new router at least I know how netgears work and I like there interface.
I hope manufactures start bringing there own Vdsl combos out as the uk is getting more and more connections like that.
The modem plugs into the red WAN socket which is also Gigabit capable. There are several VDSL routers around like the Draytek Vigor 2850n BUT you are supposed to use the VDSL modem supplied by Openreach and until that changes there is no real market.