Mentioned this a few times, but the scams calls I get these days often show my own dialling code and what looks like a valid number. Easy to think 'it must be somebody I know', and answer it.
I suppose it's not too hard, to generate a fake calling ID that is dynamically generated, with first few digits matching the called number and random digits for the r est?
Re NHS, not only do they not leave messages, but (my local surgery at least) withhold their number too, to stop people from worrying about the fact they'd missed a call from a doctor.
Funniest recent incident was from a genuine (Foreign) calling number, scam computer virus. Nothing new there. But a few minutes later another call from the same number, this time pretending to be from Telephone Preference Service, offering to help stop nuisance calls.
On a more serious note, I've heard the TPS scam is taking a few people in, worth mentioning to anybody vulnerable.