Graham,
I seem to remember something about this from a previous discussion many moons ago. I have now worked out how to correct my settings which were wrong like yours.
The settings you are talking about are in Windows and what you have is correct.
The setting that Ploppy is talking about is in your profile for this board. If you edit your profile, under Board Settings you will find that there is a time zone setting and a daylight saving time tickbox which was ticked in my profile, but if I untick it it corrects the time. I don't understand why you need to do this.
Greecemad.