Hi
My husband applied for and got the job of Census Officer, they all started on the Tuesday after the 21st so I'd guess he was a genuine caller. I think they might have started a little later and let the census returned by post come in but ONS very keen. He is working the next 4 weeks or so in contacting people and trying to help them complete or return the census. No pressure, genuinely there to help.
After that there will be another swathe of officers and non compliance officers.
Not had too much abuse so far, couple of dodgy dogs though!
But I agree, watch out for scams.
Cathy