IMHO, a lot of the large ISPs these days are much of a muchness. As is typical of most industries, CS goes to pot when they have a large amount of users and you get typical script monkeys for first line support.
Plusnet's support isnt as good as it used to be, but at least they are UK based and if you do get stuck there is also their forums. The past few times Ive had to contact support either for me or on behalf of someone else the people whom Ive spoken to have been helpful and seemed to know what they were talking about. Call wait time too thankfully seem to have improved. I psyched myself up a couple of weeks ago for a long wait as I was ringing at about 1pm and was pleasantly surprised that I got through straight away.
I was promised a call back later that evening, which didn't actually happen & instead I got a text saying it would be looked at the next day. (they had hoped to be able to instantly sort the problem with a reset, which didn't work).