This is how the UK gets it's own great firewall.

Demand online services change their services to conform to their law. Because its accessible from the UK.

Services refuse.

Up goes the wall.

I guess you don't know what actually happened. All but four of the 200 companies Ofcom asked for compliance, complied. The point is about any business that operates in the UK, and especially if it generates income from the UK, should be subject to certain laws in the UK. Not because they're accessible from the UK.