Freelander 2 Roof Bars

I want to fit some Roof Bars on my 2013 Freelander 2.
Are they difficult to fit, although I have only seen them on a car at a distance they appear to be fixed into slots on the roof.
There are many for sale on the internet, I dont want to buy some where they wont fit or will the headlining have to be removed to bolt them from underneath,
And are some better than others.
All replies gratefully received.
Thanks

The bolt holes are already in the roof channels, under the plastic trim, which needs drilling in the correct places.
Also there are different rails depending on whether the vehicle has a panoramic roof or not. Oh and many cheaper ebay roof rails are of substandard quality, and either don't fit at all, or don't fit well enough to remain in place when needed to, like in an accident.
The best and unfortunately most expensive option is to fit genuine LR rails, but at least you know they'll fit without any drama, and will remain in place when needed.

Part numbers over ere

https://www.landyzone.co.uk/land-rover/roof-bar-confusion.337914/

Not difficult to fit. Just takes time. There's a marker on the plastic telling you where to drill.