Is there an idiot-proof way of telling these two shrubs apart? 
So, I whip out Volume 3 of Trees and Shrubs hardy In The British Isles by W.J.Bean, and it appears that the name P. x lemoinei covers such a broad spectrum of hybrids, with Old World P. coronarius hybridizing with New World P. inodorus, P. pubescens, and P. microphyllus. I have a plant of the tiny-leaf twiggy miniature shrub P. microphyllus growing and flowering in the garden, could show pix if you'd like. Then, even more species are thrown into the hybrid-umbrella of x lemoinei, so this will be the harder item to define.
It might be an easier track, to learn what P. lewisii is all about, and seeing if any plant in question matches P. lewisii or not.
http://plants.usda.gov/java/profile?symbol=PHLE4