You won't need that much @glamorousindierockandroll
We do Eurocamp in France every year in August. We're a family of 4. We budget around £2000 for that.
Caravan accommodation is usually between £1000 and £1200 for between 5 and 7 nights. You can book your ferry crossing at the same time as your accommodation via Eurocamp. Eurocamp offer better rates than booking with P&O directly.
Accommodation rates vary depending on the caravan you choose. Aspect is the top range and Classic is the bottom range. The parc we go to has Lodges too. Circa £1800 for 6 nights.
The price reflects the range. We've stayed in them all over the last 7 years and would stay in any one of them again. They are all well maintained and clean.
Then it's just fuel, tolls and spending money (admittedly fuel is more expensive this year).
We go to La Croix de Vieux Pont. Tolls cost 15€ each way to get there.
We budget £100 a day spending money and we buy our food from the well stocked and reasonable local Intermarche. We don't factor that food shopping into our holiday budget as it part of our usual monthly budget (we'd have to buy food if we stayed home anyway).
We don't always spend that full £100 a day. The site we go to has a great pool and a man made beach and lagoon, so the DC spend the majority of their time at one of those. There are paid activities on parc but you can buy a card for about 70€ with an activity value of 100€ and it covers the quad bikes, trampolines, bungees, pedalos etc. We usually buy one when we arrive and the DC know that when it runs out, it's done.
Look for last minute deals too. We went to Les Ormes in Brittany in May. We booked it Friday evening and arrived on parc at midday on Sunday. 4 nights, including ferry crossing, the price we paid on the Eurocamp site was £185.
With fuel, tolls, meals out and other spending, it was about £1000 total. Could have been cheaper if we'd bought food to cook in, but we opted to just eat out for most meals.
Les Ormes is very similar to Centreparcs in terms of the pool and offered activities. Amazing pool complex.