Data SIM cards for overseas travel: good (b-mobile) and awful (Rebelfone)

uK resident here, when I travel to Europe I buy a Lebara card for each country off Amazon or Lebara themselves. They are super helpful, easy to setup for data and calls very cheap. All controlled via the browser for topups etc. If coming to UK buy a Three PAYG card as this is such a Geat deal for a fast connection and calls.