Various parliamentary immunities and exemptions already exist; extending these to include enhanced protection against surveillance would not be defining a new class of citizen. To the extent such immunities create a new class of citizen, those existing immunities and exemptions have already created it.
And, in any case, this is the United Kingdom we're talking about, a country whose government acts in the name of a monarch and whose parliament consists, in addition to a house of elected members, a house consisting of "Lords Spiritual and Temporal". Its hardly as if differing classes of citizens is a novel concept -- its already a rather overt feature of the British system.
Due to the nature of the blanket surveillance GCHQ is indulging in (tempora etc), this is impossible to do with any certainty - everything is swept up and stored. So they could pass a law, but it would be meaningless.
Positive change comes in small steps, and starts with awareness, don't be so cynical.
The UK has legally incorporated the requirements of the Charter via the Human Rights Act.
Even if the UK were to exit the EU, the UK is also a member of the Council of Europe, and bound by the European Convention on Human Rights, and discrimination under the law is also prohibited by Article 14 of the ECHR.
I believe it will catalyze the political class, such that there really won't be any way but the mainstream way from now on. We'll see political factions fade away over the next few years, until there are only a few, or maybe eventually just a couple, of the same slight shade of grey ..
They'll enshrine this so deeply in law there will be no going back without violent revolution.
That won't happen though, as the cattle are distracted and well fed - and any move against them which fails will only serve to further their interests, for you are simply a terrorist who hates the British values of suspicion, greed and prejudice.
If the opposition has too good a reputation to be called a terrorist, I.e. They're in government, famous, etc., again, easy, say they're a paedophile and nothing they say will ever matter again.
Either way, don't expect positive change from this. Expect May to hop up on a podium and explain that human rights prevent us from keeping you safe from the terrorists and so we must pass a bill that allows us to shoot dangerous people and the ten billion illegal immigrants who are taking your jobs right now, on sight, oh and by the way we're exempt from Surveillance.