Well we did it! We moved all 3 yesterday into one room, they were so excited and it was a great incentive for them to clean up and go through all their toys, books etc! We have 2 king singles in the one room for now and they will share those beds for a couple of weeks. If it looks like it will work we will then go and buy a set of bunks to replace one of the beds.

So far so good, they all slept through last night!

Re the privacy of the eldest - she has already "claimed" her old room back which has their desks and clothes drawers in and is happy to have quiet time or get dressed in there. As it really has nothing of interest in it for the younger two that should work out.

Thanks for all your advice on the situation, am really hoping that this will work out!