Sorry Sophia2457 for only replying now, I was away
You should seriously consider hiring a car; it is really the best way of seeing the country. I know they drive on the wrong side of the road with a left hand drive but you get used to it very quickly. Also there is very little traffic on the roads with the exception of Havana which even still is a doddle in comparison to somewhere like Dublin. Don't worry about getting lost too much, with a decent map you should be ok and there are those ever helpful hitch-hikers who show you the way if you are stuck; it is really safe to pick them up. Just also allow plenty of time to get from place to place.
You can fly to different parts of the island using Cubana a local airline but as we never took internal flights, it is not something I really have any information on, sorry. I have hear that taking the bus or train is a bad idea as they are often delayed/cancelled and also take hours.
Another option, but I don't know if it would be your cup of tea, is to join a group tour e.g. with GAP who I travelled with in Peru earlier this year; they are fantastic. I put their website below so you could look up possible trips. You still have to organise your own flights to/from Cuba but all the rest is organised for you. You can also organise extra nights in Havana before/after the tour. I would consider taking up this option if you are not willing to hire a car.
There are also other companies like Exodus and Explore who I believe are also quite good and they organise flights also (from Heathrow though) if you wish.
Now hotels vary a lot in standard and I would not expect much in Havana unless you are willing to pay big bucks for a place like the Hotel Nacional or Hotel Seville. We stayed in the Hotel Caribbean for the first 3 days which, putting it nicely, was a hole. When we returned for the last couple of days before flying home we stayed in the Hotel Linclon which was much better (but not anywhere near luxury). You can get nicer places just outside the city but you really want to stay in the city centre close to all the attractions. However once you get out of Havana to other parts of Cuba, the standard improves immensely and are less expensive.
One hotel I really would recommend if you are staying in Vinales (an area which you should really go to) is the Hotel La Ermita which is on a hill overlooking the valley; fantastic views.
If you are going in March, you will be fine turning up at hotels looking for accommodation without booking ahead as it will be off-peak season. But remember to book your first 3 nights as Immigration may want to see proof and I have heard of them organising accommodation for people who didn't pre-book for a hefty mark-up fee.
You connect in Paris with Air France and unfortunately it does take the whole day to get to Cuba (10 hours from Paris to Havana) but that is part and parcel of transatlantic travel. We booked on the Air France website and you don't get any better deals through ebookers etc. (we tried). I was looking at the website, depending on your date of travel costs €675 to €715. You can get flights with Iberia via Madrid for €692 but as I said before I have heard that they are a pretty poor airline.
