First of all my mistake we were on deck 10 Caribe C334 Balcony Cabin on Coral Princess
I can now answer my own question as I have now been on my cruise and it may be of interest to fellow passengers who also want to share a cabin with others.
The lower beds are separated to form two singles with a small chest of drawers between, then the upper berths which fold flat into the ceiling come down directly above the two lower. They both have one solid side to them so it's impossible to fall out and each have a guard at the head end on the other side to stop you from falling out (does that make sense) each had a ladder too although we only used one. As an older adult (46) I'm not sure that I would have wanted to sleep on an upper berth but my two kids 20 and 16 were fine and said they were reasonably comfy. There was plenty of room in the cabin for all the clothes that came out of 6 suitcases to be hung up, lots of hangars and plenty of drawer space for smalls and a big cupboard in the closet area. Bathroom too small really for 4 sharing, so we alloted one shelf in the cupboard outside the bathroom for all the toiletries and took in what we needed. We had to be very tidy in the cabin right from the start and that helped a lot. I would definately do it again though if I had to.
Sailed on Coral Princess last summer and had a standard balcony cabin BC grade on Baja Deck. It was quite a small space, no sofa just a smallish tub chair and dressing table chair so in the similar cabin for four the beds must be bunks. The shower is the smallest I have encountered on any cruise line and even other Princess ships. There was a good amount of hanging space, walk in dressing room style, but not much drawer space.
Thanks for that I have had a quick look at my booking and it is a BA grade, co let's hope it has a little more room.