New information just post July 29, 2004 on Malvaceae.info
clementii 'Kew Rose' is a seedling of à clementii 'Rosea' and is very similar to the latter. It is a more robust (to 4m) plant, growing to 4m in height. I haven't identified any single trait which can be used to distinguish it from 'Rosea', the differences being mostly if not exclusively quantitative, and of traits which are variable on both plants, depending on conditions of cultivation. The flowers and leaves, and the hairs on the stem, of 'Kew Rose' are larger, and the leaves more distinctly lobed and toothed

Here is a link that might be useful: Scroll down

If an organised Lavatera Society is meant above, would you be so kind as to point me in its direction.

hope this helps.
Check out global library to the left on IHS
also see www.Malvaceae.info

Here is a link that might be useful: societies

Malvaceae Info is my site; I'm pretty sure it doesn't have a reference to a Lavatera Society.

I don't see anything at IHS either.