It happened EU wide (actually EEA wide), as part of the EU telecoms deregulation.
While it is in general quite good, it suffers from limitations in how it is regulated that means that BT is milking Openreach for profits and upgrading the network very slowly. The whole thing could do with limits on how much Openreach is allowed to pay out in dividend based on how much they invest in infrastructure upgrades.
BT was ready to roll out fibre to the home back in the early 1990s for the delivery of TV. At the time BT had some of the most advanced fibre tech in the world.
The government of the day, however, decided to ban BT selling TV in favour of opening up the market to foreign owned cable companies, Telewest and NTL.
Without wide scpread Internet use that killed the investment case for fibre (and the U.K. fibre industry).
Today we're at a situation where none of the other players calling for BT's break up want to invest nationwide.
If they do break up BT it'll be great if you're in London, Manchester, Birmingham, Leeds but I don't expect much to improve anywhere else.
I think it's more likely that Vodaphone, Sky, Talk Talk will just try milk the existing infrastructure without further significant investment, as they currently do, and BT would be dis-incentivised from further investment.
While it is in general quite good, it suffers from limitations in how it is regulated that means that BT is milking Openreach for profits and upgrading the network very slowly. The whole thing could do with limits on how much Openreach is allowed to pay out in dividend based on how much they invest in infrastructure upgrades.