Integrated Fridge Freezer size advice

Hi,

I was wondering if anyone can advise me what size integrated Fridge Freezer I can buy to replace one that isn’t cooling.

I know the standard advice is buy the same size as you are replacing, but the one that is being replaced does not fill the space and I think it isn’t really the right size.

Here is a link to a diagram I’ve created showing the current setup. The doors sizes don’t seem to be in any of the standard ratios which is why I’m confused, but I’d like to use all the height available.

Can anyone give any advice?

Thanks

Tom.