There was one middle seat (UD A380) but this wasn't offered, plus I would have been unhappy to move as I paid £198 for me and my wife to sit together on the way back from honeymoon. Which as has been discussed at length, is a joke for J flights when you don't have status.
However, if I had experienced one of the individual issues I would have accepted it as 'wear and tear' but as the CC knew about the seat issue from the outbound, I would have throught this could have been looked at during the layover or highlighted to us and offered alternative seats in J. As I believe the lower deck was fairly empty it is likely that there were other pairs together (this was according to another CC member).