According to my experience with SEO, the most important thing that can affect the geographical location of the accommodation is the loading speed of the site. And we all know that Google and other search engines reduce sites with low loading speed (which eventually leads to high bounce rates)
The further away a user is from the site hosting, the longer it will take to load the site. However, in terms of the distance between Germany and the United Kingdom, I think that the ping (the time it takes for the loading request from the German site to reach the UK server) should be optimal, maybe around 100- 150 ms according to my estimate.
For this to be easier to understand, let's say that a UK request to a UK server only takes 10-30 ms, which means a faster loading time. Germany to the United Kingdom means a greater delay of milliseconds.
And that will negatively affect SEO scores, although I estimate only a little and not too much. However, if you have heavy assets (high resolution photos, videos, etc.), that could cause the site to load a bit slower.
I hope that throws a little light on things.