Irrespective of your legal rights, it won't help much if you win a battle with Travel O World (or the airline) in several months time if your holiday is booked for next week. So the priority has to be to find a way to get you to and from Orlando when you need to travel. So please tell us the name of the airline you were due to travel with, the planned dates of travel (in both directions), the airport you were expecting to fly from in the UK and the airport you expected to land at. (Is it Orlando, Sanford or somewhere else?). Are there actually 11 people travelling or is that a typo?
With that information available we can then research ways of getting you to Orlando because, if the flights you expected to use really are full, then no amount of hassling Travel O World or the airline will get you onto them.
Incidentally, forget about ATOL, as its not relevant here. However it's possible that Travel O World is in breach of the code of conduct that ABTA members are required to comply with, so it might be worth contacting ABTA:
http://abta.com/contact-us