Handy DIY Tip
For walls and soffits that it seems impossible to screw into the answer is to glue a piece of timber to the wall or frame (in the case of PVC window), decorate it to match the room decor, and then fix your curtain pole, rail or blind to the timber.
 

 

Plastic Cladding
2.7mt Lenghts tongued & Grooved Ideal for bathrooms Big Range of Colours (White with Silver Strips £7.99)
Price: £5.99
SKU: 033500