To be compliant with US 18 2257, as long as there is no sexually-explicit content, as defined in
18 US 2256 Section 2 (excluding part E and simulated), you should not need any documentation relative to US 18 2257.
Being that you are in the UK, and that is where any documents would be kept, I can see no way you'd ever be inspected anyway regardless of where your site is hosted.
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Standard disclaimer applies. This is just my educated opinion. I am not a lawyer.