Ah the fun and games of the broadband industry.
This does raise some interesting questions such as the more customised services BE provide.
Static IP blocks, bonded lines and I think they also do Annex M, all of which, sky don't offer.
Again, will Telefonica be handing over their RIPE assigned IPv4 blocks? Half a million subscribers isn't a huge amount comparatively (See Sky's growth rate) in terms of market share but it does raise network issues for any provider with IPv4 running out.
Plusnet has recently been looking at carrier grade NAT, BE recently had a BETA firmware suggesting IPv6 support. This will be interesting.
In my opinion Sky does a good job of keeping things simple and this has lead to their success. The majority of people just want a non strings attached simple services for a fixed price.
The problem won't be the migration it's self. These are pretty painless these days (i've been through enough to know). It'll be keeping the customers happy. That shouldn't be too bad as O2 and BE customers definitely want and unlimited service. In fact a lot of customers might actually make savings if they already have Sky TV. The main issue is going to be those static IP's... Lets hope Sky create a third package to suit them. It'll cost more but i'd definitely pay a little more for a static Address.