I know many of you will likely call sacrilege at me for this, but I recently went to the Postal Museum and went on the Mail Rail ride.
Give Royal Mail and the Postal Museum their due, they have done a good job. The only part you actually get to see is the loops and platforms at Mount Pleasant along with the depot which is now part of the museum, but you do see the start of the other tunnels, and a look down at one of the carriage sidings with stock in. Interestingly they have boarded up the portals to some tunnels and looks like they have installed a new drainage / pumping system in the now live areas. There is an audio visual show as you go, that being 50/50 split about Mail Rail and the post office in general.
But huge respect and kudos to everyone who did explore it, I never realised just how low the tunnels were, and how hot it was down there, even on a day it was only 5 degrees or so above ground.
I failed miserably though as had no camera, and even worse left my phone in a taxi earlier in the day so couldn't get any pictures which I'm seriously pissed off about.
Also, I do think part of opening this up must have been due to the Urb Ex community getting in their, so arguably Urb Ex has preserved and granted access to this for all now. Cheers!