Paper ballots in schools and so forth (day off for the kids) - take your ballot paper from the people at the desk, go in the booth and put a cross in the appropriate place with a pencil (or several ticks in several boxes in local elections), and then stick it in the box. It's a bit more complicated where there are some form of proportional representation or alternative voting (Scotland, Wales, Northern Ireland, London Mayoral), but still a paper ballot.

The count gets done manually, of course. Useful overtime for council clerks and so forth.

The government is flirting with the idea of introducing some online or electronic system, because they fancy being modern I suppose, but they'll have a job getting that through, especially with examples from America of how that kind of thing can go wrong.

Here's a government report about all this stuff.