Your on the same connection as me basically.
I run a Be Broadband 24mb ADSL 2+ line.
It's supposed to be 24mb download and 1.3mb upload.
Where I live there is a lot of line noise and Be/O2 support is pathetic.
Your best option is to buy a different router that you can use on DMT Tool.
DMT Tool is a program that allows you to manually configure your line's SNR (Signal Noise Ratio)
Usually the further you live from your exchange the higher this will need to be.
My line attenuation is 38db which is quite high, anything below 15db is very very good.
I run my line at 7.5mb and it is stable and is fast for 7.5mb. When I'm on COD I usually always get connection host due to my upload which is handy since having host gives you a big advantage over other players.
If you need further help ask me