I’d been with them years till last month. I was so sick and tired of not having 3G, or even E, and quite often when working out in country villages, which is where my work takes me a lot, no bloody signal at all. I was only on SIM only month-to-month (can’t afford new phone on contract 🙁 ) though so I ended Voda and thought I’d try each of the other networks for a month on SIM only. I’ve been on Three, and have waaaaaaayyyyyy better coverage. 3G in the middle of nowhere most of the time. The only problem is if there’s no network, you get nada whereas Voda will mostly at least drop onto a GPRS so at least you can text and call. All I can eat data too, so can use phone connected to site radio and Tune-In app for stations not available on DAB, XFM eg.
Voda were a bit of a pain getting my iPhone unlocked, so don’t go opening a new contract until they’ve done that. But if you’re not in contract anymore, it might be worth trying other networks even on a PAYG sim for a while just to see who gives you better coverage.