It means you are a very long way from the exchange. ADSL2+ does not work too well on very long lines. Phone Sky and ask them to trouble shoot you for speed. If they will do nothing ask to be put through to CST as you want your line changed from ADSL2+ to G.DMT. They will probably not know what this means but be politely insistent and ask to speak to a supervisor if they refuse. If you have no luck hang up and phone again in the hope you get a more understanding agent. After 10.30PM is the best time to call.
I will say, you will be lucky to get 1 or 2 Mbs.