You might look at Pook's Hill. It's not far from Aktun Tunichel Muknal cave. The setting is beautiful, in broadleaf jungle, and the accommodations are very nice, in traditional Maya style thatch cabanas. Hot water heat by cohune nut fires! There's a Maya site on the grounds being excavated. The owners are U.K. folks who have been in Belize for many years. Highly recommended.