To get an idea of how PR might work, I did the following:
For each Region of the UK, find the percentage vote for each party. Ignoring those with less that 5% of the vote in each region, share out the number of seats that the region currently has proportionally.This gives:
However, some regions are much larger than others, and some are over-represented (basically Wales and Scotland), so the figures are not quite what we could expect from such a system after reform, but they are not far off.
It’s not completely proportional, mainly because the 5% cut off removes the smaller parties. A lower cut-off would bring in the BNP and UKIP but it would have to be about 1.5% for any Greens to get in.