Department stores that sell curtain fabric often have a "making up service". You measure Run & Drop, select the material and ask for them to be made to your dimensions.
Our last curtains bought this way had a run of about 16 feet and a drop of about 5. The cost with lining, tapes, weights and hooks was a mere £638.
As the material comes on a long roll there is virtually no limit to the drop you can ask for - run is achieved by joining panels together.
Peccavi, May 2009
