The staircase is now installed.
The stairs came from Stairbox.com being significantly cheaper than any local joiner could make them for.
There was a problem with the initial delivery. We had ordered stairs with short newel posts for the Burbidge Fusion system spindles and handrails, but they mistakenly supplied full height newel posts for the pair that join at the half landing.
Stairbox did not quible and dispatched a replacement pair. Unfortunately only one was right, the other did not have the required rounded top detail, so that had to be re made a second time. But eventually all was well and I could complete the installation.
