Hi All I am interested to know if SKY BB Fibre will be using there own infastructure and Network & be more like Virgin who have there own Cables/Network or will they do what all smaller isp,s do and use the BT Network ? any info thanks 

I expect Sky will do what they do now, which is either lease (white label) BT equipment or install their own equipment in the exchange and use BTs fibre/cabs to deliver the service
Well its just fortunate that they own cables that run to nearly every house in the country. Another company could try and lay those cables but I doubt it is particularly reliable. Remember a lot of companies will just be renting the copper off BT.
I find its not BTs infrastructure that is the problem but their customer service!