I'm due for an upgrade soon and I'd quite like to get an LTE phone ready for next years UK 4G LTE release. I will be in the US in a couple of months.

I'm thinking why not buy a 4G LTE phone in the US sim free and then I can have it in the UK before any of the networks release 4G. I would be able to get pre-paid sim cards from the various operators and be pretty much the 1st person in my area to try 4G in the UK. Before LTE I could use it for 3G.

Are the frequencies in use for LTE in the US the same as the proposed UK frequencies? Would any handsets on sale now be good for 4G LTE in the UK?

I would imagine it's cheaper to buy a sim free phone over there anyway as we always seem to pay more in the UK for electronics.

Thoughts, problems, discussions...

No. All USE 4G LTE frequencies are different to the UK ones (Just look at the new iPad). They will not work with our networks.

Right, so the lower frequency band is 700Mhz in the US and will be 800Mhz in the UK and there are no phones that support 800Mhz on sale yet anywhere then?

It's definitely not worth buying cellular devices from the U.S. including iPads.
For example the Nokia Lumia 900 U.S. version can't do 3G on 900MHz, only on 2100MHz.
The new iPad in the U.S. has a version on AT&T that's not compatible in the UK. The Verizon version is compatible but as a CDMA device, it won't have a sim card slot so won't work on any carriers here.

The CDMA is not compatible with what our 4G networks will be either and the Verizon model does have a sim card slot for international roaming. A Verizon model works here just as well as an AT&T version but obviously an Apple Store would not be able to replace the Verizon version under warranty as they don't sell it.

I was wrong. Answer is 100% no.

I would personally wait if you want an LTE phone. The next gen LTE phones will support far more frequencies as Qualcomm (leader in the chips most mobiles use for radio) have recently released more energy efficient chips, which also happen to support more frequencies. I'd imagine say the new Samsung Galaxy (May) onwards will have these.

800/1800 for Asia
2100 Japan
2500 China
800/1800/2600 for Europe
850/1700/1900/2100 for the Americas (Sprint may move to 800 LTE! Helps the UK in a way)