Thanks The Hat for useful suggestion. I have never seen these before, done all my refilling based on Pharmicist's excellent photos which are my home page. These videos explain a great deal more. But with the advent of the semi/fully opaque carts. it is a lot more difficult to know what is going on.
The future looks even bleaker. Our American cousins who stockpiled cheap old models are really going to appreciate their foresight.
Must admit never be able to topfill without air bubbles coming out all over the place like Mikling demo's.