We arrived in Black River by public bus from Kingston late in evening, and had initially planned to stay at the Waterloo Guesthouse. But we were immediately not very comfortable there and called Ashton Great House and Hotel at the last minute (and not sure they would pick up, given that it's a family-run place and it was late, or if they would even have a room ready). But they took us in and gave us a warm welcome.
It's a very charming place and full of character (it's a 17th century house). Our room was clean too, though, unfortunately, we had only cold showers with very little water the next morning.
Breakfast is served upon request the night before. It's a bit pricey, but the food was very good (we a had traditional Jamaican breakfast of saltfish and ackee with boiled food (bananas, yams, and dumplings, with great coffee).
They also recommended a very good taxi driver, Patrick, for some excursions the next day. He took us to Black River (for the Black River boat safari to see crocodiles), to the Appleton Rum Estate, and on to Treasure Beach.
The only downside is that this place is a bit out of town (it's not within walking distance of the main sites in town in Black River). But it's in a beautiful location...very peaceful and quiet at night.