International version of HTC One M8 - 4G support in UK

[bmenaman]

Should the 'international' version of the M8 bought in the US work in the UK for LTE? The frequencies seem right according to the spec and IMEI.info - but it isn't working for me - 3G only. I've got the APN right, am in a 4G area, have selected 'LTE' as preferred network type.... I've tried it with two different networks, and 3 SIM cards

I've rooted the phone and installed standard Lollipop

No idea how to troubleshoot further so any help is much appreciated!