I'm looking around but I can't find much which I would go for. I did look at plusnet and the prices are good but the horror stories put me off.
I can understand your problem. From reading posts on this forum, it appears that even so called premium ISPs have their fair share of problems. For example ZEN's recent single thread performance issue.
I have used Sky for fibre bb and phone for 3 years now. Have also experienced line/speed issues which Sky dealt with (using BT OR) without any issues. I have also negotiated 'deals' at contract renewal time, so I cannot complain.
My other half has PlusNet fibre and phone, has also had problems with an open circuit line on 3 separate occasions in one year and her broadband speed being 'banded'.
In my dealings with Plusnet support, (regarding the banding issue), PlusNet support staff have been helpful and responsive. I wouldn't say first line support have been very knowledgeable, but with a little polite prompting have escalated the problem, resulting in a satisfactory outcome.
In conclusion my experience of Sky and PlusNet have been good (so far) as I consider my other half and I are getting reasonable value for money from both providers. If I needed a more reliable service, (maybe because my livelihood depended on it), and/or speedier support, then I would pay for premium ISP provision, but then expect excellent and timely support when things go wrong.
Just my thoughts here, and also trying to add a bit of balance regarding my experience of PlusNet support
Good luck with your quest!
ps I am not affiliated to either organisation.