I have consulted a couple of experts, and it turns out that although I took threee series of pictures in different places at different times over about 80 minutes, they were not three different butterflies, but all the same one.
They therefore considered that it was a migrant from the continent. However it not unknown for there to be more than one, and if they mate, the resulting adults (if any) would appear in the early autumn.
The picture attached to the original post was from the second series. This is from the first.
![Image](http://upload8.postimage.org/889536/2007_06_13QOSFSeries1_03.jpg)