Pse see comments below on PR. Some PR systems turn off voters.
You can't ignore 58% of the Electorate not voting. That suggests huge apathy towards a change in voting in the general population. Who knows? It may have changed in 11 years, but I doubt it.
For Reference (I have copied the whole section but addded my emphasis):
https://en.wikipedia.org/wiki/Voter_turnout#Proportionality
Proportionality
"Another institutional factor that may have an important effect is proportionality, i.e., how closely the legislature reflects the views of the populace. Under a pure proportional representation system the composition of the legislature is fully proportional to the votes of the populace and a voter can be sure that of being represented in parliament, even if only from the opposition benches. (However many nations that use a form of proportional representation in elections depart from pure proportionality by stipulating that smaller parties are not supported by a certain threshold percentage of votes cast will be excluded from parliament.) By contrast, a voting system based on single seat constituencies (such as the plurality system used in North America, the UK and India) will tend to result in many non-competitive electoral districts, in which the outcome is seen by voters as a foregone conclusion.
Proportional systems tend to produce multiparty coalition governments. This may reduce salience, if voters perceive that they have little influence over which parties are included in the coalition.[95] For instance, after the 2005 German election, the creation of the executive not only expressed the will of the voters of the majority party but also was the result of political deal-making. Although there is no guarantee, this is lessened as the parties usually state with whom they will favour a coalition after the elections.[citation needed]
Political scientists are divided on whether proportional representation increases voter turnout, though in countries with proportional representation voter turnout is higher.[96][97][98] There are other systems that attempt to preserve both salience and proportionality, for example, the Mixed member proportional representation system in New Zealand (in operation since 1996), Germany, and several other countries. However, these tend to be complex electoral systems, and in some cases complexity appears to suppress voter turnout.[99] The dual system in Germany, though, seems to have had no negative impact on voter turnout."
So, while there are some studies /analysis that suggest PR does increase voter turnout, it's only about 7.5% increase, but there is debate around correlation vs causality with other possible cultural factors at play. In the right direction for sure but I contest that figure could be achieved with FPTP and that figure of 7.5% increase is optimistic and might not read across to the UK Electorate and not enough of a justification for change, given my other bullets.
Just to repeat, I don't think PR is bad, per se, just that it offers marginal gains over FPTP and the fundamental concerns some have here over democracy don't get fixed by it.