We found out from Trehane that this is actually a naturally occurring hybrid between C. sasanqua and C. japonica (page 95). My mistake as I did not look properly for hybrids (as this is labelled as a species at Wisely). However I cannot find any other info from google other than a blank page on hortic.com and brief reference to a cultivar on burncoose. If anyone has verifiable sizes and flowering periods, let me know.

We have updated our info accordingly on our site. Apologies for the late reply on this forum (and thanks for the nice comments about the site - no ulterior motive was meant by the post!)