England & Wales Constituency Boundary Proposals are here

[muriel_volestrangler]

8. I think they're reasonably independent

Given the rules that parliament gives them (eg it was parliament, not them, who said the numbers had to be based on the electoral register from Dec 2015), they do seem to interpret them fairly, at least when I look at the boundaries around me. They follow the boundaries between local councils most of the time, and the electoral wards within them almost all of the time, and you certainly don't get the ridiculously shaped boundaries the American system comes up with.

What's happened in past is that parties put forward their suggestions, and private individuals, and the commissions will read them, and comment when they feel it's worth it (the parties' submissions always getting some comment). When you look at the parties' submissions, they can be designed to get a bit of advantage sometimes with what areas go in with who, but it's also often just a bit of signalling to electorates of "yes, we see you as a community, and we really care that you want to be the centre of a constituency, please vote for us in the next election". The parties may pay a professional lawyer or similar to write the submissions, but how much difference that makes for the commissions, I don't know.