Yes - I did delete a few items in the past. That's definitely when the problem started. However the program must be remembering the last SKU number somewhere, perhaps in an .xml file or a data file somewhere?

As a side note, when I exported my shop to a CSV file and then re-imported into a new shop, it still got it wrong. It started at SKU_0000097, when the last product was SKU_0000098

It's not an insurmountable problem, but it's a bit annoying.

Bump - OK I have at last figured this out, so am posting my solution, in case anyone is interested.

The sku numbers are held in the file products.xml. However each product also has an "internal" number (search for "internal" in products.xml).

To permanently alter the sequence of allocating sku numbers, you need to manually edit this internal number, along with the image names.

It's a bit of a pain, but it does work.

Make sure you back up your original products.xml file, in case you mess up.

Thanks for posting back Chris,

Curious, do these changes stay even if you re-publish your shop again? Seems to me any changes you made in those files would be re-written if you make any changes and re publish.