Here's what needs to happen...
UK passes said laws...
The next day, Facebook says... "hmm, ok so we can't service the UK without breaking their encryption laws..."
All UK citizens wake up to a big blue page when they try to visit Facebook that says something to the effect of "UK Citizens, you're government has decided that we can't protect our services without breaking UK laws. This means we can no longer provide you service. Maybe you should discuss this with your governors."
How long do you think it would take to either see all involved law makers impeached OR to see the H.o.P. on fire on CNN?
I bet it wouldn't even take a day (and I doubt any law makers would attempt something so idiotic again).