EUREEKA!!
Its nearly 4am and I have just spent a while, well actually quite a while using the Streetscape on Google and found it!
Its now called Thamesdown Recyling and is exactly where I thought it was, a few hundred yards nearer to Swindon than the Seven Bridges Gulf petrol station on the other side of the road.
On the streetscape the dragons teeth, big concrete cylinders with conical tops leap out at you. The place looks to have been heavily changed but the entranceway is the same.
Im going to try and link the image.
http://maps.google.co.uk/maps?hl=en&ie=UTF8&ll=51.633047,-1.830471&spn=0,0.0012&t=h&z=20&layer=c&cbll=51.632966,-1.830335&panoid=aV0QJnH-iX96KR1rC64TZw&cbp=12,214.54,,1,2.93
R