We're going through the same as you as we are having to replace our very expensive sisal runners with their beautiful black taping after only 5.5 years. Would strongly recommend against sisal anywhere, but particularly on the stairs. Any dirt, spilt drinks, splashes of water result in stains that even professional carpet cleaners cant get out. The pile is too short and it all gets embedded in those lovely ridges. They shrink away from the skirting board quickly because they cant be pinned down like normal carpet so it quickly looks tatty and we're only 3 people including an unusually clean and tidy child. If you do treat yourself please don't buy sisal!I

I am interested in this posting as our stair carpet is coming up for a change and I have started to looking at runners. I like you choice of runner. From the photos it looks like a very taught fit of the runner. Someone else would need to comment if this is correct or not.

If you have a modern home then I would go for a fully carpeted staircase. You can get great modern carpets with lovely elegant and modern textures to it. You can also add some stair rods which made it of higher quality but this would bring up your budget. There are different textures like Herringbone or striped carpets which are beautiful Cigal Kaplan Interiors

Looking at the stone, those lovely grasses and thinking about the wood, I actually think that natural coloured sisal (possibly with a stripe) brings out the blues in the colours of the woodwork, The light/dark would provide a contrast, as would the warm/cool. A rich knobbly sisal would be my choice.