Tips for using GL04P with UK SIM

During I'm visiting temporary for taking business course at London, I tried using my GL04P of e-mobile Pocket Wi-Fi device to insert UK's SIM.

There were two tips. I write for user of GL04P in abroad.

1. Necessary to buy a SIM "for data".
  GL04P could not work with general SIM for phone.
  It's a little expensive than a general SIM of buying on a vending machine of Heathrow airport.

2. Managing through a setting page of GL04P.
  At first, you should set "available" of international roaming service.
  Without that, if GL04P catch a signal but you cannot use 3G --- not indicated 3G mark.