Hilary, I am sure your ID is correct.
It is in full flower here now, having started a few weeks ago. Several butterflies feed at its flowers, and it can be quite cheerful at this time of year, but it is a problem in some areas. There's a discussion of this and other weeds, with worldwide distribution at
http://www.csiro.au/files/files/posf.pdf (a bit slow to download).
I have a feeling it is what gives me occasional days with I can barely stop sneezing, and my nose won't stop running. The usual antihistamines, nasal sprays, etc. don't seem to help much. On other days, seemingly identical, I get no sign of the rhinitis. Strange. If anybody else has noticed a correlation with hay-fever-like symptoms, please speak up!
