I think you will find that any camping electric hook-up, including circuit breakers that you buy will be 16amp anyway. This will then work with any ampage you will find in the UK or abroad.
That's interesting! Most just charge per night and don't have different amperage as a choice! Might be different abroad, but I didn't know there were any campsites here in the UK that gave you a choice!
As stated the cables are rated for 16amp, some sites do go over the top with pricing structures, some are so complicated you need a degree to work them out. And others are just plain daft.