Hi Coxy,
They're increasing and spreading everywhere in central and eastern England. The reason is a change in the law about 10 or 15 years ago, which made large landowners responsible for the illegal acts of their gamekeepers. Previously, if a gamekeeper shot a Buzzard illegally, only he could be prosecuted, but now the landowner can be prosecuted too.
The result was that most landowners instructed their gamekeepers to stop killing Buzzards the way they had been before, and Buzzards began to breed much more successfully.
The reason they stopped killing Buzzards, but haven't stopped killing Hen Harriers, is that in the eyes of these evil landowners, Buzzards are less 'damaging' than Hen Harriers. They are sadly still willing to risk prison to slaughter Hen Harriers. As far as I'm concerned, that's exactly where I think they should end up!
If the persecution of Hen Harriers stopped, we'd soon see them spreading as well . .that would be lovely. But at the moment, Hen Harriers need 24-hour armed SAS guards to breed successfully, and they still get shot the day after the young fledge and the army finish the guard.
Michael