Updated: Sep 30, 2020
The Woodland Trust site is an excellent source of information on foraging. It includes guidance for the legalities, ideas of what to forage and many recipes. It does have a month by month set of suggestions.
The key rules are – don’t trespass – forage what you know is safe – be sustainable – enjoy the opportunity.
https://www.woodlandtrust.org.uk/visiting-woods/things-to-do/foraging