We had a referendum on alternative voting in 2011. Turn out was just over 40% and just under 70% of those who voted wanted to stay with the current first pass the vote system.
Those pushing for a more representative way of voting are the same old, same old, which includes me as a Lib Dem member supporter. I think there is very little support for change outside the group who have always wanted it and little or none in the wider general public.
The electorate have always been happy to vote for both the main parties and both of them have always been divided between right wing and left wing elements, so complete unity in a central party is probably not an essential, providing both wings can come together when it matters, which the Conservatives usually do, look at the recent change of leadership, with both EU leavers and remainers uniting to support a remainer candidate, but which, sadly Labour never quite manages. Hence the election of Jeremy Corbyn as leader of the labour party and in the time the Tories managed a complete leadership election, Labour MPs couldn't even agree the rules for their leadership tussle.