Metalrail can take a bow - as it was a desire to see his photos that made me sign up.
To be clear, I presume the latest ones are at the northern end - i.e. north of where the old two-track alignment was slewed over to the east side - so the old tracks here are the mains and the new ones are the reliefs?
I take it that "Up" in this context is to Paddington via Badminton. That had me foxed at first, as I was expecting it to be "Down" from Paddington via the rhubarb curve. Is zero here at Bristol East?