Ive been told 40-60mbps, but a friend has the same package, and is a similar distance (possibly slightly more) from the exchange, and gets 35ish.
I've found a netgear product that looks like it might fit the bill. Over £200 new tho.
It looks like a bag of spanners, but I think it will do the job
Tried MHC's Suggestion of linking the cable to one of the LAN ports, I couldnt even get it to acknowledge there was an internet connection there. So I guess the netgear DG834 isnt quite as versatile as the one you MHC it with.