From London Independent – some grand days out. The only one I’ve been to is Leeds Castle, in 1990 where I stumbled upon a huge display of Bentleys surrounded by several hot air balloons.
Also, a look at St Kilda, four tiny specks of islands out in the Atlantic Ocean, west of the Outer Hebrides. Talk about the back of beyond!
SuzanneTheTravelMagpie 
I’ve never been to Leed’s castle but I’ve done a few of the others. I particularly like the fossil hunting suggestion. It’s free and involves a day on the beach!
I never actually got inside the castle – too busy drooling over the Bentleys but it’s something I’d like to do one day.