My child's DT teacher did, but they used it for one lesson, then were given it to bring home. It's now in a drawer somewhere.
That was last year. I haven't heard of any plans to repeat the exercise.
Not always. I do recognize the economic sacrifice the UK made for the sake of winning WWII. It's a beautiful thing - altruism on a national scale.
The BBC Micro cost £400 in 1981, which was £1400 in 2016, according to the Bank of England. I don't know if this includes monitors, presumably it doesn't include any software. From the other comment, you can double the price to add disc drives etc.
So, at least £400 for every 25 children. My primary school had one in every classroom, but I don't know if that was the standard, so it could be less.
A 10-pack of Micro:Bits with basic accessories come to £11 each, £275 for 25 children.