Using 4GEE Nano Sim for US TMo iPhone

[BarkingGhostar]

Anyone have any experience buying and using a 4GEE brand nano-SIM in an iPhone 5 sold by the American T-Mobile carrier while abroad (UK)? I know the handset needs to be unlocked, but I want to step away from the 2G service offering that is what USA TMo is offering in their free Global text/data and use better 4G offered by 4GEE in the UK.

For 15 pounds sterling I can get 10GB of data with text and voice on their 4G network. Mostly need it for data, but something better than 2G.