Looking at the first pic, you'll see hefty joists in place over some of the sub-floor. These now span the whole sub-floor. What is 'crawl space'? I'm pretty sure that this type of structure was never designed to enable someone to crawl around under there retrospectively.
Bottom line is, there is no way to get to any of the pipework inside the property without such severe disruption that I would take the other option of simply burying the existing pipe and forgetting about it. (bear in mind there are no evident symptoms at this point in time).
As I said, the bathroom is complete and I've just finished a really advanced kitchen project. The pipework internally has been completed to a very high standard, as has all the work, but getting to where the blue pipe connects to the stop-cock would be next-to-impossible.
As I said in an earlier post, most of what you see in the first picture is now gone. This wasn't supposed to invite critique of my work, but since you asked, everything under there is just so right now. I don't have a view of that corner completed from a sub-floor perspective to hand, but I think you'll agree that this is an acceptable overall standard and represents the quality I've employed across the renovation of my home...
...and here is how that corner looks now...
That pipe elbow seen in the first picture is roughly underneath the Chrome Laundry bin on the right hand side of the photo above and underneath the black porcelain tiles is an electric underfloor heating system, which would be trashed totally if I removed the tiles.
I've had a chat with my local Water Authority and, although I've not had an inspector round at this stage, they didn't have any concern for a connection being made to that Black ABS, providing it's done in a suitable and reliable way. They were of the opinion that it's on my property, so they take no responsibility and consequently, no real interest.
Understand that in an ideal world, I'd have no hesitation in pulling the steel pipe up and replacing it, but this is very far from an ideal scenario, hence politely asking for some help (but not just taking the easy option and pretending I never saw it).