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.
 

Wood Care

Creosote 4 Lt Dark 3.49
Creosote 4 lt Light 3.49
Cuprinol Timbercare 6 Lt Autumn Red 6.99
Cuprinol Timbercare 6 Lt Autumn Gold 6.99
Cuprinol Timbercare 6 Lt Black 6.99
Cuprinol Timbercare 6 Lt Rich Oak 6.99
Cuprinol Timbercare 6 Lt Rustic Brown 6.99
Cuprinol Timbercare 6 Lt Woodland Green 6.99
   
5 year Woodstain 750ml Deep Mahogony 9.49
5 year Woodstain 750ml Rosewood 9.49