Changing 4G/LTE Frequency topic

Hi folks,

I have tried searching but couldn't find the answer so apologies if this is covered before.

I have a 32GB HTC One M8 which I bought from Canada. I am in UK and now looking to get a 4G contract however it turns out that the phone frequency is not compatible with 4G network here..

I have read a thread here talking about adding all frequencies but I don't want to root the phone.

Is there anyway I can flash a UK unbranded firmware? Will it add the UK frequencies or is it built in the hardware.

Please advise