I believe a box of continental infantry are in the pipeline from the Perrys, so you might be better waiting for them.
In terms of the difference between F&IW and AWI British, I'm not enough of a uniform buff to know the detailed differences, but at a superficial level, British line troops in the F&IW (effectively the 7YW in North America) were still wearing the tricorn, whereas by the AWI they had progressed to the bicorne and its various informal variants. Plus the short gaiters and stockings of the AWI period are fairly distinctive, whereas in the 7YW I'm pretty sure British line infantry were still wearing long gaiters.