There are foraging courses in England - Woodland Ways does them I think.
In Scotland, it is legal to gather fruits, nuts and seeds for personal consumption, (Not for commercial purposes though) but illegal to collect wild plants or fungi on a National Nature Reserve (NNR) or a Site of Special Scientific Interest (SSSI) without the express permission of Scottish Natural Heritage, who would first require you to present written permission from the landowner.
Woodlands allocate permits to collect fallen wood but not logs already pre-cut by staff, as those are covered by the various Theft Acts.
A sensible and sensitive approach to harvesting, conservation and other land users and owners is all you really need, but there is a code of conduct on some websites if anyone is concerned that they may be stealing. (Botanical Society maybe, can't remember)
John and I used to do a lot of foraging when we lived in Aberdeenshire and we had our own fields and woodlands too, but a lot has changed in the last 10 years.
Perhaps it is similar to France in some respects but as time progresses there are more and more restrictions.