For campsites at 'budget' prices have a look at the ACSI card (
www.campingcard.com) and Camping Cheques (
www.campingcheque.co.uk) websites. There are also Touring Cheques (
www.touringcheque.co.uk) and Vacansoleil Cheques (
http://www.vacansoleil.co.uk/soleil-cheques/) They all offer a pitch for two adults, car and caravan (or tent, or motorhome), awning, and electricity for one night. Some include the supplement for one dog in the price, if you are taking a dog with you. Prices vary - Vacansoleil Cheques are £9.00 per night, ACSI between 11 and 15 euros, Touring Cheques £12.95, and Camping Cheques £13.95. Some have special offers such as 7 nights for the price of 6, or 14 nights for the price of 11.
Camping Cheques, Touring Cheques, and Soleil Cheques have to be bought in advance - and used within a year or a couple of years on the sites in their guides, between the dates when they are accepted (all information is given on the websites). The ACSI card comes as part of a book which you can buy on line from Vicarious Books for around £13.00 - and in the book is the detachable card which you use to get the discounted price on site - again between the dates when it is accepted. With each scheme you must tell the campsite reception on arrival (or if you wish to book) that you'll be using that particular discount scheme. You pay a supplement for children on top, but from your post I feel that you may not be taking young children with you! ACSI, however, on 376 of their sites, have free child places for up to three under 6 year olds.
All these schemes will give you a good choice of sites, perhaps ACSI has more in Germany, Switzerland and Italy, but it's worth looking at each of the websites as they all give you easy access to a range of sites and usually direct links to the campsite's own website for further details.
Can't help with the vignette question, sorry!