You're limited by exterior dimensions. Here in the USA, only 2-3 brand names to choose from. Marine supply and Caravan supply will probably have a couple of choices. Hope this helped point you in a fruitful direction. There should be a label inside compartment or on the door interior stating the name, model and cubic feet capacity. You may need to do a metric conversion.
We are shopping for a fridge as well.
If you go to https://www.suremarineservice.com/
You can search fridges by dimension. Just take measurements of your available space and you can see which models will fit. Probably not sensible to buy from them if you are in the UK, but you can find a local dealer once you make a choice.