You could take a leap of faith and go for a Draytek 2850n or the soon-to-be-released 2860n which will alllow you (against Openreach terms & conditions) to ditch the two box configuration currently used for FTTC installs. You could also use a Cisco 887VA-W which is a one box solution.
I currently use both these configurations and have good performance without using the supplied Openreach modem. I do, of course, keep the Openreach modems just in case there's a line fault which needs to be investigated.
The Cisco and 2850n don't have gigabit ethernet on the WAN so if you ever upgrade to FTTP they would limit performance. The Draytek 2860n has gigabit ethernet on its FTTP/WAN interface and a throughput of 330Mbit/s.