You can find the location here:
http://maps.google.com/
Just enter "Hemel Hempstead, England" and then look for the north/south blue line labeled "M1" where the east-west orange road A414 ends at it, east of the town. The aerial photos are crappy, but it appears to be in the "Hemel Hempstead Industrial Estate" northwest of that intersection.
BBC is now up LIVE... Flames still burning, skys filled with smoke, now talking about effects on fuel availability in South England..