Update
Well I've just finished my 4th conversation with the rtw desk. I must say they have been very helpful. They agree that there are two conflicting versions of the rules about the number of return trips to the ME from LHR. They have sent in a query to their one world liaison person at OW headquarters to clarify this situation. So when they have the official clarification we will know more. In the meantime I'm just sitting and waiting...