Sorry for my sarcasm above, couldn't resist!
Essentials for a short first trip probably include:
- Electric hook-up cable (if planning to stay more than 24 hours in one place - otherwise you'll manage fine on the leisure batteries). You prob only need a 15m cable in UK but may want to get a 25m straight off, or a 10 plus a 15 for flexibility. Top up the leisure batts from 240v at home, so they get a full charge before setting off.
- Camping Gaz bottle. Fit and practice with it at home.
- Levelling blocks are rarely needed but very handy when you do need them so you may as well get a pair now.
- Top-up tube/whatever for fresh water (or just fill up before you go, tank will last a good few days).
- Separate small water container if you have qualms about drinking water from the tank.
- Bedding. Tons on the forum about that - but start out with what you have at home, eg duvet and sheets or sleeping bags.
- Torch.
- Small kettle. The Outwell collapsible ones are cute and practical, if you fancy buying your van a nice present.
- Some kitchenware borrowed from your kitchen. It's quite feasible to take ordinary china, old glasses etc until you decide what fancy melamine etc you really need long term.
- Corkscrew / bottle opener.
- Plastic bucket for carrying stuff to the campsite washup point.
- Washing up liquid and a drying up towel.
- Bog roll. (I'm assuming you'll just use campsite/public loos until you're worked out your 'toileting preferences' - there are lots of options that you can enjoy researching at your leisure. But you could buy a few disposable 'bog in bags' for emergencies meanwhile).
- USB cables plus a 12v USB adapter for charging phones and stuff.
- Locking wheel nut key.
- Maybe a disposable BBQ.
- Matches in case you have an opportunity for a BBQ campfire.
- Small dust-brush for sweeping crud out of the van.
- Clothes: probably less than you think. Some kind of flip-flops / crocs (there, I've said it!) for the shower block etc.
- Towels - microfibre are great but obv. you can just take ordinary ones but they'll take longer to dry.
- Crucial: Cali manual (the one about the 'habitation equipment') as you're bound to need to refer to it first few times out. when you can't work out how to turn the gas on, etc.
And of course as much beer/wine as you can fit in the fridge. Food is optional, you can buy it on the way.
But you
really really don't need very much else for your first trip. If you buy a lot of gear you'll probably end up ditching a lot of it in the end. We all use our Calis differently so just because some people regard something as vital, it may not be for you. Travel light the first couple of times and if you're forgotten anything just add it to your list for next time.
Others will certainly add to my above 'essentials' list. I will respond with 'Doh' or 'Naah'.
Have a great time.