Risk vs benefit
Would we rather give up all privacy and have no terrorist attacks, or put up with a few attacks and keep all of our encryption ?
I would compare it to roads. About 8 people will die today on UK roads, as they do every day. The harsh truth is that we put up with this because it is outweighed by the huge benefit of roads. We do a lot to minimize the carnage, but we don't ban cars. Sorry if that comes across callous, but I am getting to a point here.
If terrorists kill up to (say) 20 citizens in the UK every year, are we happy to put up with that to maintain freedom ? Many people might say "yes". How about 100 ? Or 1000 ? Is anybody going to stick their neck out and name a number ? If a certain disease killed 100 people in the UK a year, would we be as worried, or is that different ?