After taking some more overexposed photos last night I finally got out the manual and had a bit of a look around on the web. Sure enough, there is an exposure setting on my camera that was set to +2 which was why all that unwanted light was getting in. For the record I have a Panasonic DMC-FZ20GN digital camera.
I changed the setting and took a few practise shots including this closeup of my flowering gerberas.
I like it when I successfully work things out.