Go outdoors are doing a camping stove for £20.00 atm so my DBs tell me. You might also want to invest in a camp kitchen to put the stove on and store your food. Also, wouldn't buy a water carrier, just use big mineral water holders for the holiday and throw away at the end. all collapsible water carriers are rubbish ime.
Also, use plastic-backed picnic rugs for everything. Between the airbeds and the sleeping bags, on the floor of the tent, down to the beach/for a picnic. I would make sure you take loads of blankets. You don't want to be cold at night. You dont have to buy sleeping bags straightaway. You can use duvets from home if you have the room in the car, just to see if you like camping. You also need pillows. You can also take them from home. I have now bought cheap tesco ones as they're cheaper and smaller.
You might or might not want to buy one of those collapsible, usually blue, picnic tables and chairs (£29.99 in Tesco or argos). We find them invaluable to eat from, do colouring at, play games at, but you might survive without them. We have found the tables at Decathlon quite expensive, but worth looking at.
On another thread another poster and I extolled the virtues of collapsible crates to store stuff in, like wellies, clothes, food. I also use the blue Tesco bags for stuff.
what about lights? They sell some quite good ones in Wilkinson. the ones in the pound shops are OK, but not as good quality. You might want a coupl eof wind-up torches for last thing at night toilet trips.
Crockery/cutlery. I would just take a picnic set. That's what we did at first. that meant we could use it for day trips as well as in the tent.
Can't think of anything else atm.