There's what appears to be a patched-up crack in the lintel of the colonnade in the front, which could be costly. The plastering seems to need attention in a lot of the rooms, although you cold possibly get away with a skim. The sash windows will need a thorough overhaul and some will be probably need repair/replacing.
I'd want a good close look at the (superb) roof lantern above the stairwell. If that needs work it's a very specialist job, so expensive. If it hasn't been rewired to modern standards I'd want that done. There are no pics of the cellars, which makes me suspect that they may need tanking. Is the roof flat behind that parapet? That would need a thorough going over, ditto rainwater goods.
Then you'd need a kitchen, utility, some bathrooms, total redec ... it could be a complete money pit. Bear in mind that it's Grade II*, so you'd have to get every damn thing past the conservation people, and anything you do will probably cost double what it would cost in an unlisted property of similar size.
But it could be very, very beautiful....