Many thanks for the advice ukdoctor.

I gave the call centre a ring yesterday as suggested. The CSA confirmed that there is a note on our bookings which states that we are travelling together.

The CSA said that when they (EK) change metal, seat reallocation are done automatically by their computer which cannot take account of any information held in open format text fields which is where the note was held. She advised that the only way to guarantee that we sit together was for us to cancel our existing separate bookings and then re-book so that we one ticket number.

I don’t think I should have asked how much that would cost. The response nearly gave me a heart attack. It transpires that because we have saver tickets, we will both incur charges for cancellation. In my case, x2 because I have a separate outbound and return tickets. On top of which the tickets that would be issued are flex, which means there would be a substantial hike in cost. In total it would almost be cheaper to buy 2 new return flights.

It seems that EK system is unable to link 2 Pax travelling on separate tickets, so we will just have to keep our fingers crossed that there are no more changes of metal and perhaps keep checking our bookings on a daily basis.