At least under the present system the votes are counted by real people

As opposed to AV where it's done by Martian centipedes, I imagine.

Good grief - it's the same people who will be doing the counting whatever happens. Paper ballot forms stacked up on folding tables.

As for: "Once we change, we're stuck with it for a long time." If we don't change we're equally certain to be stuck with it for a long time, pretty certainly for the rest of our lives, even for the young ones

Back in 1931 the House of Commons voted for AV, but a new Tory coalition took over and stopped the change. And of course they've been in power for most of the years since. Which is what will happen if it's a No vote this time, which is why they are funding the No campaign.