If you join wildcamping.co.uk they have loids of wildcamping spots. It is true tho that the English are very nimby and the campsite owners tend to be on the councils and so discourage any freedom as they want you on their expensive sites (one of the reasons we come to ireland every year!)
Having said that it is possible and does not have to be in industrial estates if that is not what you want.
North Devon has some car parks with about a £3 overnight charge to sleep there.
Cornwall has loads of wilding spots. Avoid in July, August. All Cornish council car parks forbid sleeping at night, some even forbid motorhomes staying, even when empty, at night...grrr.
If we can be any help, let us know...