For what it's worth, further North in the Highlands Vodafone seems to be fine for broadband (and phone also).
I can only assume the phone/broadband coverage will be comparable and if so I found O2 to be very patchy for GPRS coverage, i.e. nothing to full signal to nothing again whilst being stationary.
Having said that a neighbour who permanently uses vodafone broadband, as he's too far from the phone line for an economical connection from BT (c£8K), is convinced that his connection slows down when it's not windy!
