Your main points have already been answered by other so I won't repeat.
However, as far as the use of 4G in the UK is concerned, the new iPad3's 4G capability will NEVER work in the UK, certainly not with the current iPad3 units anyway.
Why not.. you might ask?
Well.. the answer is very simple and final, it's because the frequencies that have been allocated for 4G in the UK which are 900MHz and 1800MHz, but the new iPad3's 4G works on 700MHz and 2100MHz, so there you have it. Anyone with half a brain can see someone has cocked up big time at Apple, if they ever thought their current 4G offering would work in the UK. Our allocated 4G frequencies cannot be changed as there is no spare frequencies which can be used, other than the old now obsolete TV frequencies, and those are what the government decided on, in fact they really had little choice.
So our 4G system in the UK when it eventually gets running will require any 4G device to operate at 900MHz & 1800MHz for it to work at 4G, IOW you can totally forget about the current Ipad3's from ever working on 4G in the UK.
I assume in due course, Apple will change the hardware, to make it compatible.. ie. iPad 3 version 2...lol