In reply to MikeSilverstone:
We were there in August last year.
The Magic Wood campsite is I think £5 pppn plus additional for showers. Staying in vans anywhere else nearby is strongly discouraged and you can expect some visits from the police if you try it. The climbing there is fantastic, there's classics everywhere across the grades and it is quite a compact area. The walk in from the campsite is about 10 minutes. The campsite was cash only as of last year. You could pay by card but only at their guesthouse which is a 10 minute walk up hill and is only manned for a few hours per day. You can't book ahead for the campsite, you just turn up and find a spot. It will probably be busy in August. The pizza place just over the border in to Italy is well worth the drive.
Chironicco is more spread out than Magic Wood. There are a number of free campsites for vans at the parking for some of the climbing sectors. There are portaloos at the camping spots which are surprisingly clean. There is drinking water about 200m uphill from the main (second) car park. You can pick up the latest Chironicco guidebook at some of the shops/restaurants/hotels in the village at the bottom. The guidebook author has a healthy imagination when drawing his maps and approaches; I strongly advise using an app like 27 crags or vertical life (free trials available) so you can use GPS to help you get around. I would advise picking one of the main areas to begin with while you find your bearings.
There is probably a similar amount of climbing at Chironicco as at Magic Wood but it is much more spread out all the way up the steep valley. While you could walk between some sectors, most people drive for 2-10 minutes to the closest car park for their chosen sector and then return to one of the main camping spots in the evening. Chironicco was a lot quieter than Magic Wood.
There are more slopers at Chironicco which feel tough in the warm, especially at the low down sectors. We had to resort to night sessions on slopey things and stuck to crimpy things during the day. The higher up sectors are significantly cooler than the low down ones. I want to return in Autumn or Spring.
It is a good idea to have flexible plans and to adjust your rest days and/or location based on the weather. Most things are very quick drying but when it rains, Switzerland doesn't do it by halves.
We didn't make it anywhere else but Brione, Sustenpass and Gothardpass all look great as do many other areas. Some lower altitude areas are likely to be too hot to climb anything hard.
