Oh you don't have to go far into the sticks to find areas with pitiful signal.
Here here, without giving too much away, I'm living 4 miles away from an inconsequential town 40 miles from London; Believe me mbb is dire. Interestingly (I've tried a few) three provides the most reliable connectivity, a co-resident had to switch from EE to three because her shiny new andoid phone did nothing of use except make phone calls.