I have recently tried to install roof rails for the Freelander 2 and half the screws seem to be cross threaded/won't go in far enough to secure the rails.

I have tried new screws and still no good. Where do you obtain the actual bolts already in the roof that take the screws? I can't find them anywhere on the web?

I had to pad mine out with washers. Don't go too tight or else they snap!

I installed the roof rails myself, didn't have any problems, but took my time & used rust remover (phosphoric acid) not that it was really needed in my case, also etched primed & painted the steel with some Holts touch-up paint, you can spray it into the lid of the can & brush it onto the surface to save masking if you are lazy. Let the touch-up paint dry overnight.

If you cross threaded the holes you may want to re-tap the thread, but be very careful you don't make the problem worse, & use tapping cutting lubricant (eg, Chesterton tapping lubricant). Last thing you need is to snap a tap off in the hole. When you tap the hole for every half turn, turn the tap back a quarter of a turn. All by hand nice & square to the hole.
You may need a 3 piece tap set. Taper, intermediate & bottoming, don't rush.

To clean out the hole, hold a straw on the end of the vacuum nozzle so the hole is nice & clean, & use a pipe cleaner, the twisty things kids use, to clean the hole & thread.

Taper, Intermediate & Bottoming tapping set:

Click image to enlarge