Annoyingly my council's building control insist on triple glazed windows for the flat roof windows which bumped the cost up.
Slight change of plans. I have decided to put two Velux windows in the bathroom and not put one at all in the walk in wardrobe. As the walk in wardrobe will only get minutes worth of use a day I didn't see the point of having natural light. Also it would turn the small room into a sauna in the summer as it would be so hot. I sourced Duratec roof windows -which are made by Velux but rebranded as Duratec. They're an older style made by Velux but come in at around 35% of the cost of a Velux equivelent. So a lot cheaper
Duratec Window They come with a 10 year warranty which is an added bonus.
This roof should be tiled and weather tight by Friday or Monday at the latest.