Here’s a link to the Castle Combe accommodation pages. It’s a fairly comprehensive list of B&Bs plus hotels. If you’ve got a trailer, quite a few of the places are listed as having trailer parking. We normally just stay in the Cepen Park Premier Inn on the outskirts of Chippenham. It’s perfectly acceptable, and we’ve never had any difficulty parking a trailer there in the coach park behind the attached Beafeater restaurant.