It's hard to comprehend how these things could possibly cost as much as they do. A billion pounds to send some letters? Huh
I'm fairly sure we're having one next year over here in Eastern Europe and no way is our government spending that much on a census, we got some jet fighters for about that much...
Romania does it for 1/3 of that, 84 million Euro for 20 million people = 4.2 Euro/capita.
There's a breakdown of how it's done and the spending, too:
https://www.libertatea.ro/stiri/costuri-uriase-recensamant-b... (translate with whatever, Google and Bing are useless for me)
OK, so wages are a factor, but the UK's cost seems like it should be lower.