The Electoral Reform Society (ERS) has just published its report on what it calls the most unfair election in the UK, ever.
It has suggested that using differing electoral systems the votes would have been as follows:
Their full analysis is here.
I would probably opt for larger constituency STV (single transferable vote) as the ERS does.
What seems impossible to justify any longer is first past the post. That worked in a two party system. That appears to be history.