I submitted my tax return on Dec 25 :-) It did take a few days to get an acknowledgment, so I doubt all the taxmen work through Christmas...

I got a ‘you've paid too much tax, here, have some back’ letter once! It was handwritten as well (but back in 1992ish), to say ~"In the last few years you have claimed a tax refund and I wanted to remind you in case you wish to put in a refund application for this year"~. As it happened I didn't, but it was nice of them to ask.