Was sure we had a thread on this, but can't find it.
2 ways to do the sums, either by adding up the amperage of all the items, or the wattage.
I use the wattage as I find it easier for the sum, and gives a bit of scope. Others will think different, but there we are.
At 10 Amps and a supply voltage of 220V (you won't always get the 240V you think the supply is, so err on the safe side in terms of the sums, not the electrocution risk). So in total you have 2200Watts available at any 1 time.
As you have a leisure battery, use lights, TV, phone chargers that can be charged via the 12V circuit. Your solar panel if fitted will keep the battery topped up most days, even in the winter. At night the charger will draw power if required.
The heating will generally have 3 settings on electric supply, 1Kw, 2Kw & 3Kw. Therefore the 3Kw is not available as it draws 3000Watts. At 1Kw it draws 1000Watts, 2Kw draws 2000Watts of your available 2200Watts. So if you put the heating on to warm the van up using the 2Kw setting you can't use the microwave (800Watts), kettle (750Watts) or hot plate (750Watts), hair dryer (1200Watts) etc whilst the heating is on. Once the caravan is warm, turn the heating down to 1Kw and you can use the microwave on it's own, the hot plate on it's own.
When you want a shower put the heating/hot water to 2Kw for 15-20 minutes should give you sufficient water, then drop it to 1Kw. When you finish your shower turn the heating off and use the hair dryer, then turn heating back on.
Your fridge draws very little power, so it can stay on all the time.
You'll soon get used to watt you can and can't do. The only time we've tripped the supply was on our first winter CL trip where we had the heating on 2Kw, then put the microwave on as we were trying to get everything done at once. Lesson learned, girls edumacated on what could go on when, job done.
Using gas is an option for faster warm up on the heating, or boiling a kettle. But as you've paid for the electric in the pitch fee, then use it.