I believe either my g-g-g (or gx4) grandfather was one of those Hessian mercenaries, but he settled in New Jersey.
I would like to clear up one point: though these Germans were called 'mercenaries,' they really were not--not in the sense of individual soldiers of fortune. What they were, however, were mostly German farm boys who were drafted into service by their local prince to fight in whatever war the prince directed them to. In order to make money since these German princes had fallen on (relatively) hard times, they rented out their soldiers to the Brits for the war against us. Although the Grenadiers and others were professional soldiers, most of the infantry were not.
For those interested, there are places where you can read some of these "Hessians'" letters home. Many have been translated, but many are still in German only.