To clean or not to clean, that is the question

Hi all!

Thought I'd pick some brains...

I'm a very part time manager of a very part time theatre venue at a UK 
festival (its a church for the rest of the year).  After many incidents
with 
food, water and blood packs (curse Popcorn) the time has come to get our 
black drapes looking black again.  We tried getting several quotes for tab

cleaning, but this cost basically as much if not more than getting new
tabs 
made.  The drapes are the backdrop to each of our 4 stage areas, so 
represent a significant investment.

SO...

Does anyone have a reliable way of cleaning then re-proofing (most of the 
tabs are Boston Twill so NDFR) which is significantly cheaper and as 
reliable as getting new black tabs made?  We find that we can get Wool
Serge 
tabs for not much more than it would cost us to clean our current stock.

Names and contact details of any suppliers or cleaners in the UK would be 
very welcome, location not necessarily a big issue.

Thanks in advance,

Tim