When I was looking into this for MORERC last year the company's I was given were as follows:
http://www.charleslawrencesurfaces.co.uk/ - Contact: David Fearn
http://www.mcardle-astroturf.co.uk/ - Contact: John Kirkham
I have their numbers/emails if you want them - can PM them or they're on the websites I think.
Good luck with the track, site lloks perfect - I'll definitely be there when its done.
Ben