As another commenter said, nobody in the UK is going to protest over this. As a downbeaten kingdom (in my opinion), we have no fight left in most of us. People will sigh and move to another app en masse.
The issue I have with all of this is that we think a law is going to make people who break the law not break the law.
The only people who this affects is people who everyday people chatting to their family.
The ones this is claimed to be fighting don't, by and large, use WhatsApp and the like, so will make no difference to how they operate. The one off they catch who does naively use it, does not justify surveilling the entire UK.