Four birth fixed single beds?

A brief look has thrown up a few possibles on Autotrader website, so you might need to look at a few options and then ask for exact bed dimensions. Four fixed beds and you are likely to be in the almost 8 metre long category. Good luck.

Try Caravanfinder where you can search by layout.

https://www.caravanfinder.co.uk/caravan_layouts.html?berth=4

The 4 single berth versions seem to be rare animals and will be hefty long vans when you find them.

A layout that comes close might be the Sprite Major 6 TD, it has two fixed bunk beds at the back and the other seating can easily be made into singles to sleep 5.

We have one and certainly the front singles and rear dinette are adult size while the bottom buck is a little narrow it will take an adult. The top buck can take an adult but it's quite difficult to climb into. We now use it as a three (sometimes four) berth with ourselves and grown up children.

see here: https://www.swiftgroup.co.uk/caravans/swift-sprite/