Here is my recommendation on places to visit in Cuba:
1. Habana ( I stayed around near plaza Viaja, in Habana viaja. Casa perticular in Habana is around CUC 25 per day.
2. Vinales - 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 Cauo Lavisa. ( 4-5 days) You can spend ages in vinales.
from vinales you can take a bus to Trinidad.. ( great City), base yoursel here and go around santa Clara, pay of bigs, playa ankon.. .. (4-5 days )
3.Take a bus to Santiago de Cuba.
I have heard there are few good dive sites around the south coast which i didnt explore but sincey ou have time you might want to go there..
days 3-4. Music here is fantastic..
4. Barocoa- its 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 atleast 3-4 days in Habana.. if you can spare $60 go visit tropicana.. worth it. You can also go to les matanzes. Veradero 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 in the receipt when you sign..
If you have breakfast there its 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 thats 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 hitch hiking is common. I met few tourist who had been only hitch hiking across cuba..