Had sky fibre for 2/3 months, started at 42 and went down to 15, seems a common issue, also had 2 routers in 2 months becuase of constant disconnections, sky support are keen but cant do much, really its all down to open reach and their lines, bottom line from sky was if my issues are not resolved we may get a discount or released from the contract.
Open reach bods say will most likely have the same issues with any ther provider, really miss virgin, they suck but the cable is fast and very stable.