Random suggestion regarding sky speed issues. While I work for BT, this one's just something I caught in passing talking to a colleague (I'm going to Virgin, so hopefully helps dissolve a little thought's about bias. I'm a contractor too so no share worries).
Sky won't guarantee speed, BT do. While I was at my previous address (middle of Sheffield suburb) I never failed to get the 73Mb my line could support.
Where does it say BT guarantee speed but Sky don't? Both providers are subject to OFCOM's Voluntary Code Of Practice which states that within 90 days if your ISP cannot provide the speeds initially quoted prior to sign up after going through their technical procedures then you have the right to leave without penalty.
OFCOM also just said that Sky have the most consistent speeds at peak times.