When I was with F9, they were the residential arm and Plusnet only dealt with business users, both being run as separate entites, so I was lead to believe. To my mind, that is where the split was as they had totally different customer bases. Once PN began to accept residential customers, it was the beginning of the end for F9, the same as it was when they acquired MAAF. They were swallowed up by a bigger fish and suffered service wise as a result. That is of course, all in my personal opinion.