My customer service experience is limited to Vodafone, Three and O2. Like @jonsie I found Vodafone customer service to be the worst (I dont like being laughed at when I phone to say I don't have service 
), Three and O2 have both been ok - so far!
I'm not overkeen on the Priority app as there doesn't seem to be much for me. I used to use it a lot for Dominos but as I don't eat pizza now there isn't a lot else!
