I say no, we have enough European governments with proportional representation already.  Should not someone allow for the possibility of more decisive action?

Estimates are suggesting that Labour won two-thirds of the seats with one-third of the vote, more or less.  So that induces the usual cries of misrepresentation of the electorate (it also reminds us that virtually all electoral systems are not "democratic" in the naive sense of that term).  But Britain has many serious problems, and I would rather see one party given a decisive mandate to handle them.  And I write that as someone who is not in general rooting for the Labour Party -- virtually all of my favorite British politicians are Tories, even if I do not like what that party has become as a whole.

Contrast the British with the recent French election.  The distribution of votes was not altogether dissimilar, but the Britsh have "a landslide," while the French have a possibly ungovernable situation.

I do love checks and balances, but the UK needs to defeat NIMBY and fix the NHS.  Now it is Labour's turn to try.  Here is a broad outline of Labour's 100-day plan.  Not exactly what I would choose (see Wooldridge at Bloomberg), but if they get two or three big things right the regime still could be a success.

Note that the margins for the Labour victorious seats are extremely low, which means there is an ongoing constraint on the exercise of government power.  I am not so worried about an "elected dictatorship."  If anything, it may not be decisive enough.

Another consideration is that PR for the UK could end up meaning the rise of an Islamic party of some kind, of course with minority status.  I suspect that would worsen rather than improve democratic discourse in Britain, and perhaps hinder immigrant assimilation as well.  I don't want that to happen, and so it is another reason why the UK should not switch to a PR system.