I was involved sourcing astro turf a number of years ago I got the off cuts and waste from a new school hockey pitch. Astro turf has a limited life interms of hockey and tennis courts were it is most commonly used. You just need to make contact the firms that install them. They will be paying to have the old stuff destroyed so will happily give it to you.
Google is your friend there loads here were the first two that came up:
http://www.go4grass.com/contactus.html Preston or
http://www.artificialgrass.org.uk/ Chorley