Thanks for the comments guys.
the stack I posted is one of half a dozen taken. I was not overly happy with any of them and had a few more goes the next day. I agree with the comment on composition and got out the nail scissors for the second go and took off a couple of the stamens.
Apart from the clutter, when you stack, having one element in front of another can lead to artifacts which are not easy to deal with.
As to the technique- I have used Combine ZP (free), Zerene stacker and Photoshop. I have not tried Helicon but am aware of it.
Since CS6 and the cloud- my first choice these days is Photoshop as I can stack raw files and I only shoot raw.
Steps for Toni-
In Bridge select your images to stack then
TOOLS>PHOTOSHOP>LOAD FILES TO PHOTOSHOP LAYERS
Then after they all load to Photoshop, select them all then
EDIT>AUTO ALIGN PHOTOSHOP LAYERS
then EDIT>AUTO BLEND PHOTOSHOP LAYERS
And you are done- except for the tidying up. The techie bit is easier than the artistic bit !!!!!! ....john