Another problem you will probably have is that they've changed a lot of teh drainpipes from the sturdy cast-iron jobbies of teh thirties to new plastic ones. And I don't trust a plastic pipe to hold my weight...
And yes, I ahve been wandering around Cambridge looking at drainpipes. There's a promising one in a certain location, though, but I'm not going to tell ayone about it as that may well be too irresponsible!
Other routes are off limits now too. For example, the Caius library which is mentioned and described as a starter route has its front face floodlit, and so that's impossible to climb.
In short, nightclimbing is a lot harder than it used to be...