Sadly as the internet develops and living our lives online becomes more the norm, e.g. banking, shopping, storing photos and documents, it becomes easier for governments to monitor us. I think you would be naive to think that there are not people within government agencies/the security services whose job is monitoring social media. You only need to think of the algorithms which influence what comes up on your Twitter feed or on Facebook to realise that certain views or words will trigger interest in your posting.
All governments do this so don't think it will stop if Labour get into power. Their targets may just be slightly different.
I do however think it is appalling that this has been used to stop people from speaking at conferences if they hold ant-government views. This is definitely something people should be concerned about as it is only likely to get worse.
Don't forget that the UK has one of the highest incidences of surveillance cameras in public places in the world. You can be tracked easily by bank card spending, store loyalty cards and countless other methods.
Whilst we go about our lives normally this is not usually an issue for most people. The problems start to arise if someone does something which, although innocuous to them, flags an interest in those carrying out monitoring. This has always happened throughout the ages but it is just a lot easier to do now.