Tips before buying drapes

Use a reputable company specialising in soft furnishings.
They employ people of high standards, often with interior design experience. They will have a wealth of knowledge of fabric composition, colour, styles and practicalities.
Get a written guarantee.
Whilst you are covered by the consumer guarantees act, you should always get a guarantee of workmanship and quality.
Get a budget established before starting.
To save you a lot of time looking at product that may not suit your situation. Custom made curtains and blinds are almost always dearer than ready-made products.
Don't pay for quotes.
You don't need to. Companies who charge for quotes may tell you their expertise is more valuable than others. This is very unlikely, if not misleading.
Comparative quotes.
If you get more than one quote make sure that you are getting "apples for apples". In other words, make sure it is the same fabric, lining, style, meterage, and tracking. You may find the dearer quote could be the "cheaper" quote if the same product was quoted on.