If AV would have led to more coalitions, as most people think, then it would hardly have been "tinkering" "in a small way". For a start, if we'd always had it, it seems likely that we would never have had Thatcher. Pretty big difference, I'd say.

The point of AV was that it was more democratic, not to make more people vote. That's a separate issue.

PR is not relevant either, as we weren't offered it. We were, however, actually offered AV. We had a chance for a more democratic system and we said "no". No co-incidence that Oxford and Cambridge voted for it.