You can achieve a good level of light protection with venetian blinds but not true blackout shading. The nature of the way in which the blinds are constructed, means that even though the slats are designed to overlap each other a fraction when they are tilted into the closed position, there will always be some light penetration filtering in between the individual slats.
We also offer, Louvolite Perfect Fit, designed to fit inside uPVC window frames. Available in Venetian, Roller or Pleated styles. Drill-free non-intrusive installation ideal for rental properties and home owners alike. Each blind comes with an integrated frame that consequently provides a stylishly seamless look.