Following a discussion on another thread that touched on servicing the motorhome (waste empty and water filling) whilst away.
I thought I would tell you all how I do it when using wild spots and CM stopovers.

Firstly I search out places like West Beach Hayling island, Canterbury park and ride because they have 'aire' style facilities provided.

Secondly I email CM stopovers to ask if I can stay and of there is any chance of servicing the motorhome, I make it clear all I need is a loo or a manhole and a tap.
90% have been positive and willing to help.

Thirdly. Commercial campsites, I have used 4, just pulled in and explained what I need and ask if there is any chance, each time the person I have asked has put a bit of change in their pocket and been happy to allow me in for 15 minutes.
I have found the larger and busier the site, the happier they are to allow it.

Fourthly, shops and garages etc.
I have asked when buying things if they know anywhere I can fill up with water.
'What do you need' is the reply I hope for.
3 times I can remember putting my hose over fences to outside taps they have.
The last one was in Tintagel Cornwall, the hardware/camping shop next to the car park.

For me I'm just cheeky and ask but always respectful and expect nothing and it seems to work!