Re: Not wishing to trust Big Gov, but--
"Pressure your MP for the introduction of a simple ID card, make it clear that this should NOT be linked to any backend systems other than a record of who you are."
Bad idea. It will simply be taken as an endorsement of what they actually want and the proviso will be ignored. Far better to make it clear that you do strongly disapprove of their attempts at universal surveillance and that includes ID cards.
Only if and when HMG has shown it can be trusted should you push for ID cards if you consider them to be a good thing - which, frankly, I don't as a matter of principle.