Correct, the 4G ipad 3 doesn't support the 1800Mhz band therefore 4G isn't mentioned on the apple ipad pages on the UK site.
The iPhone 5 added support for the 1800Mhz range so it can do 4G from EE and 3. The other networks 4G won't be in the 1800 Mhz range and so will never support the iPhone 5.
Kris
Sky Fibre Unlimited
Ashington (Northumberland) Exchange