Wiggum: Sky's whole model is outdated. They should just scrap satellite completely, and convert to internet streams over broadband, with an IP type set top box.
You obviously have no idea how much Sky would pay to Akamai to deliver VOD to all their 500k customer base.
The satellite delivery is by far the most effective way to deliver serial the to the masses.
Netflix deliver around 100GBit/second for 80k customers or so. To do that for everyone assuming everyone had decent quality broadband it would require further significant upgrades to a whole lot of CDN nodes.