Well finially got round to getting some roof rails.
Looked long & hard at the non-genuine but as I want to 'use' them - I finally ended up with original fitment.
Many thanks to Famous Four - very helpfull & prompt.

Always wanted to go with black finishers & silver rails.
Being a black car (non black pack), that then followed the same silver highlighting on the lower doors panels.

Start to finish - took me about 2 hours - I wanted to take my time to get things right.
Old roof finishers were removed first.
They came off a lot easier than expected - every last clip stayed fixed to the finisher, all of the foam pads too stayed stuck to the finishers.
Must admitt I was amazed how much dirt there was under the old finishers.
Gave all a good clean.

Loose fitted the brackets to the roof (well made items)
Offered up the actual rails - to see the best alignment - there is some back to front play.
Once happy I used the provided plastic alignment blocks & tightened down the brackets.

Next was checking the replacement finishers for alignment, these had several sticky foam pads & several serated fixers.
To be honest there was not much choise where these went as the serated fixings can only go in one place.
Unpeeled the sticky pads & stuck the finisher down.

On to fitting the rails - again very loose fitment first, again still some front to back movement.
I found it was good to get up my steps an extra step, so I was higher so I could put some downward pressure on the rail as I tightend up the bolts.
Adding this bit of pressure helped lock everything together.
Important note being make sure the rubber gaskets are in the right place on the underside of the rail feet - this can be fiddly as when you turn the rail over to offer it up to the brackets the gaskets can keep falling off.

Once everything was tightened down & all looked straight & ture - clip in the 3 cover plates to the sides of the rail feet.

Have to be honest I did the same job on my Disco 5.
Main difference was that the rails had the fixings coming down through the rail itself - so the only cover plates were on the top of the rail - you couldn't really see them.
These side covers (L405) were a little 'weak'
I really wouldn't want to have to remove them - I suspect they will break.
Thus make sure your happy with the total fit up before fitting these covers.

Click image to enlarge

They look really good.
I was thinking of fitting silver rails, now I am convinced. 2018 SE SDV8 4.4 Byron Blue

I think that looks amazing. It's something I wanted to do on mine once I've got some confidence back in the car and the coolant leak fixed.

What bars did you go for? 2018 SE SDV8 4.4 Byron Blue

Those look very smart

I wonder if you could have the bracket covers colour coded to the paint so that the silver rails "floated" above the roofline  2021 D350 Fifty Edition - Carpathian Grey
2017 4.4 SDV8 Autobiography (2021-2024) - Santorini Black
2012 4.4 TDV8 Westminster (2016-2021) - Santorini Black

The cross bars I use are Thule aero bars with the appropriate feet.
The bars end up about 3 inches wider each side than the rails.
These feet allow the bars to be placed anywhere along the length of the rail.

I find that useful for different length items.
Example with a long ladder I prefer to support the ladder with the bars as far apart as possible.

Only thing to watch out for is still allowing enough space at the back for the boot to open - if needed !!!

Are they 1.35m or 1.5m bars? 2018 SE SDV8 4.4 Byron Blue

1.5m