anf - for a natural (bushy) look it's got to be a mixture of native British species, stuff like Hawthorne, Yew, etc. (also great for wildlife). Trouble with using this lovely stuff is its not very, very fast growing. If the hedge is to be clipped REGULARLY and has to be fast growing then there is only one contender, I'm afraid it's the Devil Himself - Leylandii Hedging. My own favourite for any hedge has to be Pyracanth - evergreen, thorny, flowers, and the birds love the berries; fast growing and happy in poorish soil. The 'elf & safety lot might point-out the danger to the local hoodies of the thorns - but it will be secure.
How to provide a little security whilst the shrubs grow: erect a deer netting fence, fixed to driven-in timber stake posts, interweave the plants through the netting.