I was in a similar situation with Sky. Their boxes continually failed, then after the 3rd attempt to fix within a 3 week period they told me I would have to pay for an engineer visit. Rather than try to appease the customer for the inconvenience of having to wait in for an engineer to replace their faulty kit, they decided to charge.
I cancelled and went Freesat on a Humax box. I don't miss a single bit of Sky.
They do keep sending me offers though that are getting more tempting each time. Last one was for a 1TB HD box + Multiroom + all packs inc HD, Sports and Movies for 25 quid a month for a years contract.
Still, I won't be returning.