This is an interactive version of a map showing a possible proportional representation based allocation of seats, using the results of the 2015 General Election.
Note that this map is currently resource heavy, and will be updated to use a more generalised (less detailed) set of constituency boundaries.
Seats are allocated prioritised by overall national party vote, with candidates ranked by share of the vote within their constituency (the first seat allocated is to the Conservative candidate with the highest Conservative local vote share, second seat to the Labour candidate with the highest Labour local vote share, etc). For details see: http://blogs.ucl.ac.uk/dis-blog/2015/05/11/what-would-the-country-look-like-under-proportional-representation/. This isn't necessarily the best way of allocating seats, but it's easy to do, and is quite useful for showing where parties might win more seats under some form of PR.
Seats are coloured according to the allocated party, with varying transparency based on the share of the local vote that the allocated candidate actually received.
Thank you Adam Dennett for the boundaries for this map and for the catogram boundaries used in the blog post linked above.