O2 had hopeless coverage for me in angus, maybe better elsewhere? Vodafone used to be great coverage, could take calls sitting on the sofa, but during 2013 it got much worse, it is again a scrabble to run up the stairs to answer calls whilst while hanging out the bedroom window if want to hear what the persons saying.
However, in their favour, today they replaced a SIM card for me after my phone was nicked in USA. No charge, all very easy. So thank you Vodafone.