I am making an educated guess here.
I have Wassell pipes, bought a cheaper pipe to replace some road rash - the new pipe fell apart. The "Norton" branded pipes look exactly like the cheaper pipe I had (thick welds at the taper to the pipe), so I am making the assumption that the Andover pipes are the cheapo's with Norton stamped on them. I could be wrong, of course.
If anyone knows, please let us know as I need another full set of pipes (no not road rash, another bike!) and want the nice Wassels.