Jos: Today I had a call I might easily have fallen for. The caller said "This is Matthew calling back in regard to the government-funded insulation - lagging you've had installed up in your loft area?" [presumably a question as the intonation went up at the end]. The accent sounded like south-east England, maybe someone who grew up on a London overspill estate. It was totally convincing apart from the fact that my loft insulation has been there for about 40 years and has no connection with any government scheme.
I had exactly the same call on the same day, also from Matthew. Never found out how he was trying to scam me, because I just said "no you're not" and put the phone down.