EE currently has deployed LTE in their 1800MHz spectrum and they will relinquish some of this (2 x 15MHz) to 3UK by the end of 2013 when 3UK can deploy their own LTE services.
Generally the minimum requirement to deploy LTE is a requirement of at least 2 x 10MHz, so the two lots of 2 x 5MHz may cause EE and 3UK issues, so they are considering joining their efforts and sharing their joint spectrum, giving them access to a joint amount of 2 x 10MHz.
Currently this is just in the planning stage and it may not be technically feasible, though there is no reason why it shouldn't be.