I've not used it. But met them at NEC when caravan & motorhome show was on. I'd get it if it was an app but didn't want another book, I've got all the aires France. I flicked through the book and it didn't seem as nicely laid out as the French version. It's free camping as the pubs etc. are hoping you eat and drink in the establishments suits me.
An app would work very well for this I've got it to find some cheap / free spots around the coast for a few weekend one nighters!