People who oppose proportional representation often imagine that all you’d get would be hung parliaments consisting of the same parties that we have now, so that the only possibilities for forming a government would be a Labour-LibDem coalition or a Tory-LibDem one. I can see why that wouldn’t appeal a lot to supporters of either Labour or the Conservatives.
However, many countries with proportional representation have more parties.
Imagine if that happened here.
The Tories might split into two, the moderate One-Nation Conservative Party, led by Ken Clarke, and the Thatcherite anti-EU Conservative Party, led by William Hague.
Labour might also split up, perhaps into Old Labour and New Labour.
And the LibDems might revert to the days before the Alliance, separating into the Social Democratic Party and the Liberal Party.
Suddenly there would be many more ways to assemble a majority The One-Nation Party, New Labour, the Social Democrats and the Liberals would all be able to work reasonably well with each other, so depending on electoral fortunes, at least a dozen different governments would be possible.
Yes, it would more often that not give more influence to centrist parties, but that’s normally a good thing for a country.