I've made a last minute change and decided this is a much better case study than Keyhaven, which is frankly a bit useless. I've left Keyhaven though, if anyone wants to use it.
General
It's a bay in Dorset in the south west of England.
The majority is sheltered from highly erosive waves, but the southern end is being eroded.
There are sandy beaches around the bay, with sand dunes and heathland behind them.