The Main tree I'll be using is the Oak. There a couple of reasons for this. It's quite an iconic and easily recognisable tree that people associate with the British countryside. It also has very varied trunk shapes that can be used to provide lots of visual interesting. The leaves also provide a nice range of colours as they fall off during Autumn.
I'll have to use some other trees for variation but I think the Oaks will be the 'Character trees' the focus of the wooded areas.