Velux loft Window extras necessary?

[gasbusters]

Hello all

I'm looking to install some Velux loft skylights but a bit unsure of what kit I actually need.

I've watched some videos and they say you need the following

-Velux window
-Velux tile flashing kit
-Insulation Collar
-Vapour barrier
-Underfelt Collar

I've contacted a supplier who say I only need the Velux window and tile flashing kit. But all the videos seem to suggest I need the other 3 extras.

Can someone clarify what is actually needed? The loft where the windows are to be fitted will be converted into bedrooms.

thanks in advance