B & Q day and night blinds size adjustment 

Cutting day and night style blinds down
Remove small Philips screw from top frame
Pull end cap off
slide blinds out
Mark top frame to the width you want cut with a jigsaw use the original end you cut off as a guide to re drill a new screw hole
using a pencil, mark the blind to the width you want and draw a neat line full length of the blind cut using a new Stanley blade and metal ruler mark the blind 30mm shorter than your top frame width
mark and cut the roller tube the same width as your blind
cut the weighted bar 10mm wider than your blind width job done hope it helps someone thanks