-
It can actually be a bit of a grey area if occupied for protest
Really dependent on the scale of things and how the courts/cops a feeling about it I think
I don't know the law, so that may be right, but obviously in this case we don't know enough to say what's going on. With a house like that, wouldn't you expect staff to live there permanently, so that it wouldn't be unoccupied? Also, did the protesters just enter it to protest, or did they claim squatters' rights? I'd guess that they could be removed in either case, although I'm sure it may well be more complicated than that.
Squatting residential property was criminalised by the ConDems in 2012.
https://en.wikipedia.org/wiki/Squatting_in_England_and_Wales