PlusNet had an awful time a year or so ago. They learned from that, and I've found them reasonable lately. They're among the cheaper ISPs, and to some extent you get what you pay for. I use them in the Norfolk hideyhole.
My main ISP is UKFSN, who are an Entanet reseller. Quality is better, and they are dearer.
If I had to pick one, and didn't mind paying £20 a month, it would be any of the Entanet resellers. If I wanted cheap, it would be PlusNet.
Next door neighbour is with TalkTalk, and wishes she hadn't done that.