In reply to Jimbo W:
Fellow plant and tree enthusiast but live in the South so don't think any of my limited plant knowledge would be relevant. Your patch and what you are doing sounds fantastic, especially having access to a stream and damp introduces some interesting possibilities. Try the RHS forums for advise.
For the cover shrubs I'd suggest doing lots and lots of cuttings or buying small plants, or wait for next winter's bare root season. Rowan (Moutain Ash), Bramble, other berries, Hawthorn, Blackthorn (sloe) may be possibilities. Willow and hazle like the damp and can be coppiced. Hazle cobnuts is good source of food for mice etc.
I'd take advice before you turn over or improve the soil, some of the grasses and flowering plants you want may fare better on ground that's not been much improved.
Good luck, would be good to see some pictures... (UKC gardening forum?)