On Monday, 3 August 2020 12:14:16 UTC+1, wrote:
I know someone, not currently accessible, who has a tall fridge/freezer and a short freezer. The first is at least 12 years old, privately imported from a europlug country. The second is recently acquired, I know not how. The installation instructions are not likely to be found.

I think that the backs of them are too close to the wall.

I found no guidance in the FAQ.

What would be a sensible separation to suggest?

If the width is towards, but less than, 600 mm, I'd assume they were made to occupy a standard kitchen unit space each.

(Similarly with depth.)