Wasn't there last weekend but I've done two overnights at Briar Hill over the years and shadow figures in the east corridor near the old hydrotherapy wing are pretty well documented. What you're describing isn't new. The question is whether you're seeing residual activity or something that's actually aware of you - because teh behaviour is completely different and most people can't tell the difference on the night.
Did any of you get photographs or video? Even poor quality footage is worth posting up. There's a specific technique with long exposure on a decent camera that can sometimes catch movement that your eye registers but your brain dismisses. I've had results there before that I still can't fully explain and I've been doing this a long time.
If anyone's planning another visit it's worth coordinating properly rather than just turning up. Would be interested to hear more detail about where exactly you were standing when you saw them.