Thanks for your patience re the strange looking left sidebar yesterday and today. Needless to say I've learnt a lot from the experience! As you can see I've switched templates to solve the problem and then edited it to regain the 3 column layout.
I hope you like the new look: I'd been thinking the old one might not be too good for people with red/green colour blindness anyway and so changing colours was on my blog to-do list. Yesterday's problem meant it just happened a little quicker :)
Many thanks to those of you who left supportive comments, helpful ideas and links to useful stuff over the past couple of days.