Skill Test
You need to do the rating training and skill test with an JAA TRTO, then you can do all together, f.e. doing an FAA Rating, JAA Rating and skill test (if the TRTO offers FAA training as well!), without additional hours on type. If you have more than 500h on the type on your FAA ticket, you can do the skill test without additional training. But in all cases you have to do it in the UK, because CAA doesnt send their inspectors abroad. Thats my experiences, good luck!