Have a look at some of the British forums, the poms are regular visitors to Cuba and it seams to be one of the "top of the bucket list" places for them.
If you google search flyforums uk you will find a good site with a heap of info in the salt fly section including lots about the different outfits offering fishing. Avalon has a lot of the fishing tied up so can charge what they like, but there are other independent guides and resorts.
Hope this helps.
All the best.
Mike