I have had cable for the last five years, no problems found with it at all. One outage when the water-board cut through the cables and put us all off but this was fixed in less than a day. I have noticed a drop in speed at some peak times but the 4mb service normally speed tests at 3.8Mb. As I cant get broadband from BT's old copper wiring (some of Strowgers original I think)I will be continue using cable for the time being.
When I had cable installed the engineers were extremely helpful as to running the cable where I wanted it and left me a long loop of slack under the floorboards in case I needed to reposition my box at any time. I connected the PC to the modem installed the program and it all worked first time.
Cant help on the question of Sky - never had it so don't know how to get it turned off, but you may have to give them a months notice.