Only half the battle
The thing is this is only half the battle, because say every single home in the uk is connected with fiber great. That cost x billion's to do, but now ether your connection will be slower than before, or your price for broadband will shoot up.
The reason being is the backhaul and centrals as mentioned in the article. If the current centrals/atm backhaul is left in place, ISP's wont have enough bandwidth to offer even 8mbit because there will no longer be people who get less due to loop loss limitations. Instead everyone will have faster pipes and will demand more of the same size pie. Some exchanges are already stuffed just on VP capacity. I talk to people getting 800kbps throughput on their 8128KBPS sync line (7150 BRAS) and nothing can be done because the line is performing according to BT specs.
So ok BT upgrade the backhaul (probably as part of 21CN), great now the bottleneck is in your ISP's cetral's, if the providers has to get more to keep up then cost's go up to the customer or more and more aggressive traffic shaping has to be applied to mean that the network doesnt choak.
You then have the issue of the ISP's core network, most ISP's core network link's are not as fast as people might think because not many people are maxing out their links 24/7, but and increase on bandwidth is going to mean investment in faster core network's.
Then last of all there's the peering, more peeringing will be needed to carry more traffic which while not the greatest expense is still yet more ISP level cost increase which at the end of the day will end up being passed back to the customer.
Im expecting a customer install cost of fiber at around £1k and average monthly price for high bandwidth line over this (not traffic shapped because thats just lame) to be in the £100's. Its a price id be willing to pay but I doubt most of the UK would.