Eliza, I don't know where you're from or how much time you've spent in the UK. We love the Cotswolds and have been there many times, usually staying for several weeks. Although we've stayed in other villages and have also done some long-distance walks, we usually now stay in Chipping Campden. It's a wonderful village and doesn't have the coach tours you find in some other villages. The bus service is limited, but with some planning, you can make it work. (It's more set-up for local people than for tourists.) There are also local taxi services and you could plan ahead to utilize those, perhaps to drop you off at Hidcote / Kiftsgate and then to pick you up a few hours later. (I can recommend a few drivers.)
I know Eleanor has visited many castles in the UK, but we have taken our groups to Sudeley Castle for years and people really do like it. It's privately owned and there's something for everyone... history, gardens, beautiful countryside. And you might enjoy visiting the town of Winchcombe as well. I wrote about Sudeley Castle recently in my blog:
A Cotswolds Experience: Discovering History and Gardens at Sudeley Castle
If you end up staying in Chipping Campden (or even just visiting for a few hours), I'd suggest a meal at the Lygon Arms and lunch or afternoon tea at one of the tea shops. Also, the Cotswold Wardens do guided walks a few times a week, which would give you a great insight into the village-- they just ask for a donation. The Tourist Office will have info on this.
Kathy