My Negril home away from home is Miyard. The upstairs room facing the ocean is my favorite. Nice breeze, great view from the porch, ceiling fans (it will not be hot this time of year anyway), lots of hot water, and it is right there at Miyard. It is a convenient location and very affordable. There are also two cottages.
In Treasure Beach I have stayed several times at Irie Rest Guest House. I don't know what the rate will be this time of year but in the summer it was $40. My room was actually a bedroom with bathroom, plus a full kitchen and nice screened in porch. Like many places in Treasure Beach it does not have hot water, however, the water tank in the sun usually makes the water somewhat warm. It is a short downhill stroll to a nice pretty private beach.
I am very envious of you. I had hoped to be there over Christmas, but family duties prevent it.
Have a great time.