With a fixed double and bunks it is unlikely to be small.
Tabbert do a few fixed bed/fixed bunks I think, the Rimor 530 had fixed double/fixed bunks also
Do you want fixed bunks? Are you buying new or used? What is your budget?
I have seen a few 6 berths with fixed doubles and a side dinette that goes into bunks, no UK manufactured fixed bed plus fixed bunk layouts come to mind but I will have a look.