Hi - I contacted the Safemove team. If you contact them on 0800 1 385 385, Monday to Friday you can book a 30 minute session on their computer at their Head Office. Didn't find that they had much in the way of detailed maps - I knew more from going underground than any of their maps showed. There must be detailed maps somewhere, possibly the council, but I didn't want to pursue any further in case my enquiries raised too much suspicion and it started to be difficult to get into the tunnels. Someone definitely maintains the tunnels so there must be maps. I have now explored all of the underground tunnels including going up some of the big obvious vertical ladders and others less obvious. and matched some of the underground vertical shafts to the man-hole covers above ground, by walking above ground. A good fun place to explore. Let me know how you get on.