Dear Mike,
This is a tough one, as far as I know Cotham had three locations,the first I assume Cotham,the second where I went Durham Park,the third I don't know !!
The photo's of the building is Durham Park on the "Downs"(where Mr Burgess executed me). To get to it you would go up Whiteladies Hill and at the top go straight over the roundabout (left is the zoo) and go straight on pass the "Glen"(where Mr Phil tried to kill me)and take the first right and first right again. The school was on the right. I think Gerry Warriner worked at the first location but I didn't meet him until I went to Quantock.
I've enclosed a few more photo's.

All the Best

Laurie