Jim, RHS does not list any hybrid with that parentage. Your plant is simply GORGEOUS!!
About the L. purpurata - to put it into perspective, please have a look at Mauro Rosim's post on the subject.
http://forum.theorchidsource.c...
He talks about the fact that there are more than 150 varieties of L. purpurata!! Take a look at his selection and read on.
Btw here is no such thing as the "real purp",
but there is such a thing as the 'tipo'/type of species. In the case of L. purpurata it is described as " having white petals and sepals and a purple lip".
(And in addition, perhaps growing under higher/lower temperatures may even cause small changes in shade?)