We have a trailer tent, so similar to a folding camper. Having camped 'properly' for eeons, it did take a bit of getting used to the trailer tent, there are a few differences.
We don't have a carpet, occasionally if it's cold, we use 2 very large picnic rugs but we have found the awning groundsheet a little thicker and therefore quite warm.
The whole tent is bigger, so it can be much colder than a normal tent, plus there are gaps where drafts get in. However, you can cosy in an area if needed at night.
We have fold out beds and I have found them as warm as sleeping on the ground (if not warmer?). But our mattresses are quite thick, so maybe something to check.
We're able to keep a lot of stuff in the trailer, both big items like tables/kitchen unit and small like gubbins. This has been our main difference, on a camping trip we now just* pack clothes, sleeping bags, food, a few bits and bobs and head off. Likewise on return, not having to put camping stuff away in loft/cupboard is awesome.
We bought a few bits to keep in there- it has almost been like kitting out a second home. But we do use it a lot 5-6 weeks at least every year, so useful to have stores or washing up liquid etc left.
We got one last year, it's very roomy but cosy too. The main problem is packing up wet. We have so far avoided this although we did have to stay an extra night in Cornwall last year to dry off. If you pack away wet you have to open it up again a day or two later to avoid mould.
There is a Facebook group - The Trailer Tent and Folding Camper group. The people on here always have plenty of useful advice.
If you are not confined to school holidays, join ACSI. We have booked some amazing French campsites really cheaply. They are all €13-19 /night for pitch, tent/van, 2 adults and electric! We even booked one of the UK sites in Cotswolds, ready to pay £15 as forgot it was €15, and their exchange rate was very much in our favour! It's also a great way to find sites not generally advertised here. If you book a ferry, the camping clubs always guarantee you cheapest price too.
The ACSI discount is for low season, so up,to about 10th July depending on site, then from Sept. However, the app is still useful for finding sites, allows you to email the sites in English and gives links to their websites. A lot of the municipal sites are listed. (App is payable though if you are not a member , but only a few pounds for each country)
I would recommend the ViaMichelin free app for route planning. Tells you the toll free routes so you can compare, and we have always found it accurate, allows you to gauge how far you can go.
Some, but not all sites cover Easter. Most sites seem to be open 1/4 - 31/10 with discount from 1/5 - say 4/7 then 1/9-30/10, but other have discounts from 1/4. They all decide when to offer the discount, but we are booking with one site with no discount, but because we liked the site having found through ACSI. We are off next week for 2 weeks, staying at 4 sites, 3 with discount (costing 13, 15 & 17 euros a night all in each!) the 4th site is costing 168 euros for 5 nights, but is on the beach on an island. Not sure if I would have joined though before the kids had left school and we were free of peak season only holidays.