I would first like to say I'm very like Mr. Green, in that I am a retired engineer. I do have one grandchild, but I get a good night's sleep.
My notes are quite brief. I want to summarize them quickly, and before I give them, I will paraphrase Winston Churchill: The first past the post system is the best system, except for all the rest. I've written down proportional representation pros and cons, and first past the post pros and cons.
The pros for proportional representation are that it elects more female parliamentarians. That's been proven many times by OECD countries that have proportional representation. It elects more ethnically diverse governments. That's again justified by other jurisdictions. It maximizes the preferential choice of the voting public, and hence creates policies more in line with the wishes of the greatest number. If we had a proportional system in the United States, we wouldn't have had the Iran war with George Bush.
It reduces the possibility of a government being elected as a majority with less than 50% of the vote, unlike 2011 and 2015. It increases the possibility of a coalition, and hence promotes checks and balances on the major party, as with the vast majority of OECD countries. It reduces the possibility of hyper-partisanship—this is somewhat speculative—such as heckling in the House, nepotism, backroom dealing, and lack of transparency. I think it would improve that situation.
Finally, it would improve environmental performance, like Germany, Denmark, Holland, Norway, and most other European countries, which are far more advanced with their environmental policies.
The cons for proportional representation are that it's not perfect, but like many people have said already, all the other ones are not perfect as well.