Hello, thanks for responding. I've looked at the photo on the website you mentioned and I don't think that it is Helma. The written description mentions reddish veins and brown spotting. My plant doesn't have either of these - the brown discolourations in the photo are damage caused by over-enthusiastic bumble bees. I have some higher resolution photos which I will post shortly.

The flowers are a slightly greenish cream on the reverse, paling to cream at the edges and in the interior. Each tepal has between one & three ribs on the reverse which is downy. The stamens are yellow..