First time camping, we have spent the weekend away with eletric hook up. Next time we are trying a site where there is no electric.
We have a leasure battery which is fully charged, I know the lights turn on when no electric is connected, so assuming its coming of the battery.

Will the 3 pin plugs work as normal from the battery?

How do I connect 12v items to the battery, The round plug types.

Hope this makes sense!

You need mains power to put a 3 pin plug in. The battery only operates the lights.

Sorry. missed second question. The round 12 v conectors can only go in cigerette lighter of car / van. We brought cooler that runs on 12 v for when my boy goes karting ( no mains power. ) You could buy a genie but its depends how much power you need.
Hope this helps you.

So the lights will work, so I need to sort out a cool box. If I get one with a 12v plug, I dont want to touch the car if possible as its dads car, also I think the keys have to be in to power his cig lighter!
So how can I master the coolbox plugging into the battery thats in the trailer tent?
Also mum wanted a hair dryer - any ideas?

You can get a socket to connect to the battery so the 12v plugs will work but the battery wont last long and forget useing a hair dryer it will eat the battery power.
If you need all the items that use power then go on a site with a hook up.

you should not need a cool box has most caravan fridges run of the gas has well as mains and car battery, they have done this since the 70's, simplest way to remember is no sockets so every thing you use that is a household appliance will not work unless you have a mains supply. you will have gas only if no mains and you can get some 12volt tvs, we did from comets but if you ask them they will not know . Ours run on a transformer and you will only have about 8 hours of power before the batteries will need to be charged from the car