Neil, that's probably the most elegant and clever DIY tool storage system I've ever seen. My brother has been thining of a tool shelf for him, that's definitely the way I would build it for him. I could also make him a few extra metres of that "shelving" with the groove planed in, so he would only have to saw them to shape and drill holes for tools if necessary.
That's clearly ready straight to commercial production. Did you invent that yourself or did you see something like that somewhere else? It would be brilliant as a product: just two different components (horizontal strips which could even double as verticals behind them, and then blanks for the tool shelves) and a bag of screws.
There have been many good examples on the thread, but this is definitely the best.
Pekka