Re: It's not broken don't fix it
We were NOT offered PR, at least not in any meaningful sense of the term. Additional Vote is window dressing for keeping First-past-the-post, and electing a least worst candidate.
Real PR is single transferable vote in multi-member constituencies, which introduces reasonable proportonality whilst retaining a link between MPs and a constituency, albeit a larger one. It's not perfect but it's much much better than what we have now.