Thank you SO much, Elusian for your post. This gives me a greater understanding of how to use the HTML overlay filter and your code is very useful to me - I will experiment with it when I get some time.
I understand the HTML and CSS part of the code - the WebVfx part is a little above my head right now but it gives me something to investigate. The scrolling is very smooth. Well done and thanks again for your time doing this.
Best wishes
Jon