I am able to adjust the headrests in my Citreon C3 Picasso, however there will be less support to keep the guard in place with the headrests lowered.

No, all the fittings provided need to be used with a headrest. You would need to get a guard with the support legs.

Hi There. I have fitted this guard to both the front and rear headrests ofmy car. The brackets are designed to fir on headrests regardless of location int he vehicle. I would recommend you try this on the your front headrests as i am 98% confident it will fit - Keep your receipt though as Halfords WILL give you a refund if it doesnt fit.
Hope this helps?

Yes it fits my ford focus 5 door hatchback very nicely.

Yep - fits my shogun fine

I think so, it has two side extensions that you can add if needs be, if the scenics got headrests and a solid seat back then it should fit the gap

We put it on a Skoda Fabia hatchback but also have a Micra and I am confident it would fit that too.

Its universal and has extenders in the box too

should not be a problem as the fixings can be mounted anywhere on the grid, thus it can be adjusted down very easily

Yes it will easily fit.