firehawk - yes i missed that you are on EE contract entirely.
but the point remains valid, it has to do more with the bands and spectrum of each provider. How do I know this?
about 18 months ago, I got a nokia device to test (in Pakistan). The official launch had been pushed back for 1 month already and they were still not ready to release it. After a lot of pestering, I got my hands on the device before its launch. I popped in my SIM and it worked just fine. I played with it over the weekend, wrote a review and then sent it back to Nokia.
They still didnt launch it for another 6 weeks. Why? Their official 'reason' was that they were experiencing network problems with some of the mobile network providers and couldnt launch till they were all ok with it. Considering that there are about 4 providers in total and none of them on anything vastly different from each other (such as GSM, CDMA, LTE mix) I couldnt see what their problem was or why would it be complicated.
Anyhow, the EE story rings in the same tone which is why I think they are actually on a stop gap solution of an EE only firmware that will work 4G. If I were you, I'd ask EE to give me a free Lumia 920 handset to work with their pricey contract (i am assuming you are paying a lot)