Something that hasnt been mentioned yet is air conditioning units.
I was staying ar Erw Lon once in Llandovery, nice place, folk wear clogs.
We were fortunate to find a pitch that would accomodate satellite signal and pitched up, as the night went on we became very aware of the huge monstrosity that we were next to, it was one of those humungous things that can only be pulled on the back of a lorry hitch, like a Carnival trailer.
They were fine, didnt see the people but the constant click and chug of the air con unit every 15 minutes drove me nuts, i was glad we were only staying for 2 nights.
I guess its not really an inconsiderate thing to have air con, but if its clearly audible from all corners of the site (it was because i checked when i walked the mut) you would think they would turn it off at night.
Worse though was the sound of all the clog wearers strolling to the shower block at night, i mean, for gods sake people, we arent in bloody holland!
Good site and good owners though, no complaints there.