Sky I think is fine but mostly for people with combined tv packages who get a good bundled price.
I'm with Sky atm (just ADSL, no TV, no phone), and have been since they inherited me when they bought O2. Never had any technical problems to speak of, and the one time I needed to talk to customer services they were fine.
Once I've got a handle on what FTTC/FTTP options are available to me, providers and prices etc, I'll approach them as an existing customer looking to upgrade (G.fast is supposed to be available now or very soon) and see what deal they can offer me.