My experience with their fibre service was bad customer service with very long waits, broken website and IT and a pricing model that meant you had to call them up every year to threaten them just to not get a 50% price increase. Service reliability was alright though.

After switching to Plusnet all of those problems went away, and I can get through to a person in less than a minute most of the time, and both times it has been someone in the UK. The price rises a small amount each year (£3 I think?). They have done some weird clerical errors though were they have accidentally cancelled my contract twice over the course of 2 years. Still better imo.