Roller blind material needs to have the fibres in the warp and weft fixed together in order to ensure that the blind will not skew when it is rewound onto the roller. ( Particularly noticeable with narrow 2' x 7' drop blinds) This is why it feels stiff. A heavily dressed fabric will have the same performance as long as it does not get too wet.
I've copied this from someone's earlier post to give you the details:-
They're actually called Alban Blinds. They don't have a website, according to their ad in the Yellow Pages, but can be contacted on 01727
844822 or 01234 824440. They have a stall in the Snorbens Market (Wednesdays and Saturdays). We bought the awning on our office window (faces SW) from them 7 or 8 years ago and are very happy with it.
Hope this helps
Regards Capitol