Had friends go snooping inside Hellingly Asylum, seems like a wonderful place to explore if you're into it. We used to snoop around Shoreham cement works + quarry (disused since the early 90s) until last year when they started employing security to watch over the place
I love these kind of places, they're so atmospheric and alien, it's a great sensation being inside them. Unfortunately they're bloody hard to find and since I've moved away i've not found any abandoned buildings.