Hi shaun,
i don't know if you already got the aswers to your questions but i well know south Brittany especially near La trinité and Carnac.
In fact i registered to this forum only to answer you. ;-)
So, around La trinité, you will find many opportunities to dive with commercial organisations or not.
I don't know your skill and your tastes, but normally you'll find something to match you needs.
Commercial orgs are :
- in La Trinité : "Made In Blue" . They are good and can bring you to all the interesting spots around.
- in Carnac : there is two, the first i have forgotten the name is in front of the main beach in the basement of the hotel "Le Plancton", the other located in the rear of the nautic center is again "made in Blue".
If you like "Bio" diving, you have two great spots in the Etel ... river. Yes in a river! Just located 300 to 500 meters from the sea you will find an extraordinary variety of sea specimens in less than 20 meters. And you dive for free, cause you don't need boat, you begin from the river bank!
Mail me back if you're interested. Diving on these spots is a bit tricky, cause you have to kow the exact palces and to be really well synchronized with the "marée haute" (i don't know the english word), but it worth the pain, really.
For great sensations, you can also try a "dérivante" in the "Golfe du Morbihan (only with commercial org, cause you need a boat, unless you got one). It's a diving around -30 meters in the flowd. You have very less to do, only enjoy the view and guide a bit. The water flow do the job for you. (The boat drop you at one end of the "golfe" and pick you up at the other end, simple!) I'll try it in the first week of august. The last time i asked to Made in blue, they said me that they organize this diving every Friday afternoon around 6PM. check it.
There are also 5 or so sunk boats, and finally the island Houat, Belle-île ... And the Lorient Submarine (U171 i believe). I will dive on it in the beguinning of october.
I don't know if i will be able to dive in this area during september. May be a week-end, but feel free to contact me.
Regards.
Jerome