I want to replace some fairly transparent Velux roller blinds with blackout blinds, and also install blackout blinds on Velux windows that don't currently have any blinds (and which are quite high up so probably a professional job). I notice that the official Velux blinds are way more expensive than Velux-compatible blinds made by other companies. Does anyone have experience with the non-Velux blackout blinds - are you happy with them? Is it better to get the Velux ones? Thanks!