Sleeping bag, remember you're going somewhere warm, so not too heavy, a cheap one will do. Get a liner for it, something in fleece is good, the just use the bag as a duvet, I.e. put it over the top but don't get in it. That way if you get too hot you can throw it off. If it does get cold you can get into the bag properly.
Take an airbed, cheap ones about £10, a thermarest or such is great, but you're somewhere hot, so comfort is more important. If the cold is coming up through the ground, put your outer clothing under the airbed. A blow up pillow if the airbed doesn't have one.
Tent, get a 2 person tent, gives you just that little bit more room to move about in. Which means you can be a little less organised about what you keep in the tent. Keep an eye on the shop 'Great Outdoors' they have some great deals at times. Do not get one of those tents that 'spring' open. They don't fold up small enough. And DO have a go at putting the tent up before you go, and yes you do need a degree in origami to get the bloody thing back in the bag it arrived in, so if you can, get another, preferably waterproof, not to keep the tent dry, but to protect everything else if it gets wet.
Take a pee bottle, there's nothing worse than having to blunder about a camp site at night. Size of the neck is optional as long as you can get Mr Wriggly right in there, you do NOT want to spill it or miss in the tent.
A torch or lantern, a headtorch is good. Some cord to make a clothes line and make repairs.
