Pepe
I can see from your response........

I hate to state the bleedin' obvious, but the best way to find out if it'll reach outside the window is to try it and see...

that you are an eminently practical man whilst I am just a dreamer..................MikeT

It is a wise man who recognises his own strengths, whilst accepting the weaknesses of those around him ................... a paraphrase from the musings of Ambrose, a long since passed beachcomber from Walney Island. MikeT

I didn't realize the 'shower enclosure' could leak water into the floor and chassis. I rinse the floor of the washroom and just assumed the water drained down the plughole and out of the van.

On a recent trip to a campsite without facilities we took a pop up shower tent and a hazelock portable shower filled with one kettle of boiling water and two of cold. It worked a treat although next time I'll take a small wooden duck board to stand on.

When we lived in our Eriba whilst our bungalow was being built we used a toilet tent with a hozelock portable shower. Same ratio of hot and cold. We used a shallow builders bucket to stand in and watered the garden after.
Should have clarified, not this Eriba, in those days we had a PuckL, no facilities. Porta Potti was in the garden shed, that worked well until the builders discovered it.

We use a toilet tent and rechargeable shower with its own small submersible pump. Amazon sell them for about £35. Just fill a trug with warm water and off you go. It takes very little setting up and we used the same set up when we had Motorhome with its own shower as everything was just sopping wet after using it.
I'm not suggesting that it's the most pleasurable showering experience ever but it's effective though. If you purchase a couple of those solar shower bags that heat up in the sun you've got free convenient hot water on hand too.

https://www.amazon.co.uk/Suaoki-Portable...e/dp/B01DP7CW0A

Jez, that's brilliant - I can see an upgrade coming on!