It sounds like an area which would love woodland edge plants such as primrose, bluebells (true English not Spanish), wood anemone, wild garlic and so on (maybe not foxglove as it's poisonous to livestock, but so pretty). Wild roses, and various shrubby native trees such as hawthorn, rowan, one or two elder, all carry flowers and berries the bees and birds love. If you can afford it, using plants rather than seeds for the flowers tends to be more successful. There are some good wildflower suppliers around and their websites often have good advice. What you don't want is 'wildlife meadow' plants.
If you intend to use animals to keep the grass down, research a bit to find when they should go on and off.
Put up some bird boxes too - you just have time if you send off for them now, otherwise put them up in the autumn.