Don't think you need much else. I've got the same one and the only slight problem is plugging things in all three plugs at the same time, because of the way the plugs 'sit'. (Try it and you'll see what I mean!
Easily got roung by buying a couple of double adapter plugs and plugging them in first
Yes Lyns, that is the correct type of tent hook up lead with circuit breaker and RCD.
As andysstuff says, due to the socket covers opening vertically you may need an adaptor or short extension lead if you wish to plug in a phone charger or mains adaptor.
No that is fine to plug directly into the campsite mains supply. As others have said with some plugs (chargers and the like where the plug is large) you will find that the lead clashes with the next plug in the row of 3 beacuse the sockets are arranged vertically. In EHU's where the sockets are arranged horizontally the leads stick out of the side of the EHU and does not interfere with the next socket/plug. All you have to do is be a little specific with which plug goes in which socket to ensure the best fit.
------------- Nigel
March 2012 - Dove Meadows
6th July Moving to Hayle
Lyns, I have recently bought the same Hook up lead and used it for the first time this weekend. Its excellent - very long lead, complete with circuit breaker - we had high winds and heavy rain but no problems. I would agree with taking another extension lead with you though, as I took a fridge and instead of being able to leave it in the kitchen area, we had to have it in the living area. Extenion lead for me next time.