Call off the search party!! I received a nice response from the private seller on ebay, who has confirmed that he doesn't actually have one with two removable panels (although he thought that was what he had bought!!). Seems that the Mk2 with one removable side panel is the most up-to-date version, other than the new Tour model that Simbob2004 described in #43. Back to the drawing board!

You may notice quite a few adverts for these say “erected once”!
We found it a bit of a struggle.
Firstly, it’s essential to clean out the channel first and lubricate with silicone.
https://www.amazon.co.uk/dp/B006UCNI38?r...asin_title&th=1
Note that this is not the normal WD40.
Next, unless you are tall and strong, you may want something like these steps
https://www.amazon.co.uk/dp/B00B8TTXPA?r...ed_asin_title_1
These steps are brilliant by the way and we wouldn’t be without them.
We are on our second trip tomorrow and hoping it’s all a bit easier!