Here is my recommendation on places to visit in Cuba:
1. Habana (Havana) ( I stayed around near Plaza Viaja, in Habana Viaja. Casa Particular in Havana is around CUC 25 per day.
2. Vinàles - Bus ride from Habana.. This a valley and from here you can go to two different diving sites. 1 to the west tip of Cuba ( Marina Hemingway) and 2 Cayo Lavisa. ( 4-5 days) You can spend ages in vinales.
from vinales, you can take a bus to Trinidad.. ( Great City), base yourself here and go around Santa Clara, bay of pigs, playa Ankon.. .. (4-5 days )
3. Take a bus to Santiago de Cuba.
I have heard there are a few good dive sites around the south coast that I didn't explore but since you have time you might want to go there...
days 3-4. The music here is fantastic...
4. Barocoa- it's worth a visit.. great little rundown old city.. 1 day (Editors note the region surrounding this area is superb take more than a day if you can.)
5. Back to Santiago de Cuba and a bus to Habana. you need at least 3-4 days in Habana.. if you can spare $60 go visit Tropicana.. worth it. You can also go to Les Matanzas. Varadero I hear is too commercialized and then was a gated community.
Accommodations while in Cuba
I stayed in Casa Perticular most of the time..they usually charge $CUC 20. See what they are writing on the receipt when you sign...
If you have breakfast there it's usually $3 and dinners are usually $7. I had most of my lunch in a Peso shop where you can get a sandwich, refresca for a $. So that's around 30 - 35 and spare $5 for evening beer which is usually a $. So I think 40 -45 is realistic, which equates to around £25-30.
transport is cheap and hitchhiking is common. I met a few tourists who had been only hitchhiking across Cuba.