Well I certainly learnt a lot there tonight. The Basil did not come to life until around 1996 which would be why it is not in your leaflets this far. The original James was a metal tank Henry, but I am not sure if it was the type with or without cordwinder, or indeed both as time progressed. At least one Wendy was a metal tanked cleaner and was exclusive to the Machine Mart chain of stores. There can't be that many around. Also there have been cleaners labelled Bernie, and Bertie, and James of course saw a reappearance in recent years. One such example appeared in a Littlewoods catalogue and was purple with purple painted tubes, just like the Basil cleaners had been painted in red, green, blue, or yellow. I don't know if this model was exclusive only to Littlewoods or not.
I have never in my life seen of a William or David. One would guess that the plastic tubes were not seen as a selling point. Do you know if it was a cheaper cleaner than Henry, and if so by how much? It can't have been much cheaper I assume. I assume also that Henry was the more popular choice and that Numatic dropped the David as a result. I can't see it being that cost-effective to have had the Henry and David on sale together.