Cheers guys - I've managed it.
My DVD burner is supposedly a 16x write speed model so the first DVD I copied to at that speed. I then tried to check the results by viewing some of the images in the various folders using XP's picture and fax viewer. These were mostly OK but the viewing process stalled on some of the folders - the viewing window opened OK and some of the jpg thumbnails loaded but some remained inaccessible. I'm thinking this was simply due to the presence of the mov. files in these folders which are a) quite large compared to the jpgs and b) can't be read by the XP reader but would welcome any feedback on that.
I've since removed all the various mov. files to a separate folder of their own and copied the original folders onto DVD using 8x speed and the problem seems to have gone away. So all in all I'm pleased with the results.
One final thing though. I've never used DVDs before and the top surface doesn't seem to have the same sort of user labelling area to write the contents on. What's the easiest way to label the DVDs I'v created - they will be going into labelled plastic sleeves but I'd like to mark them in some way to avoid confusion.
Thanks for the help as always!!