After a bit less than four years in the ground, the bush is now around 2.1m/7' tall and about the same diameter. Robustly healthy, with almost no care taken at all. It has mostly been left to fend for itself. Currently flowering its head off in the middle of winter.
Re the gales mentioned several years ago: the bush got blown over on its side by a howling southerly while still quite young. It just lent on some of the northern canes and kept growing. I figured I might as well let it, since if I tried to force it to do anything else it might get worse damage from the next gale. This has turned out well. It has just kept on growing and more or less sorted itself out for form.
Cut all the dead wood out of it yesterday, including getting right under the canopy at ground level. It's quite an easy rose to work around providing you are careful. I was wearing a long-sleeved shirt, but no other protective gear. Came out of it with all limbs still attached and minimal loss of blood.
Not so tall and whippy now. After the gales we've had recently, I thought a shorter stature would do it good while it got itself sorted. Still plenty of plant left, so it shouldn't sulk, and I now have a few Tillier cuttings in reserve.