UPDATE for anyone, and @Lucas and @willwood
I’ve just made a small change to the test page: I removed the animation from the opening of the menu, and the page is no longer jumping back to the top. Demo of this is here (page2): http://bikeboxni.com/gateway/page/
The original test page with animation applied, and so the issue still present is here: http://bikeboxni.com/gateway/
The only difference between those two pages is the one that works has no animation, the one that doesn’t work, does.
On the original page (now with the password protect removed): http://bikeboxni.com/ I tried removing the animation from the menu opening, but it made no difference. However, there is still a lot of other animation on that page (scrolling links etc.) so again this makes me look towards a JS issue.
I would appreciate if you can both look at this with fresh eyes. I appreciate your comments back to me via email, and it’s all valid, but I really to find a solution to this, or if one can not be found I need to look at changing my tools. But that is the last resort for me.
All feedback, from the devs and/or anyone else appreciated, I’m totally stuck at the mo!