I would just like to mention that changing your caa licence over to an faa licence is not just a short matter of paper work .
when I arrived in florida my licence still had not been approved even though they told me that it was on the phone before I left which ended up with me being unable to fly till I had a meeting with the faa in ft lauterdale .
In total It took me two months to get that letter of authenticity that approved me to fly in the US .
my advise would be just to go over and sit the faa ppl flight test and then your dual rated . The test Is pritty easy , it costs $250 and its much quicker and easier than going through the paper work with the caa/faa ..flighttime ..