So I went to Wikipedia to confirm my suspicions…see below. I like the bit about how the site is growing over and reverting to the original primeval English countryside, sort of a green and pleasant version of a lost Mayan temple:

“The Teletubbies’ landscape is an outdoor set located in rural Warwickshire, England, at Sweet Knowle Farm, Redhill Bank Rd, Whimpstone, CV37 8NR (between Stratford upon Avon and Shipston on Stour, close to the River Stour.[3][4][5] It was reported that by 2002 the set had become overgrown, and pending the 2003 lease expiry it was expected to become farmland again.”