It's a while since I posted but The K&WR is still alive!
I've been doing a bit of maintenance lately. Some of the ballast has crumbled away... again! I've tried different fixing methods this year. Some I have used diluted waterproof PVA and when dry gone over it with the usual Astonish Wood Floor polish, time will tell. On some sections I have dribbled thin superglue onto the dry ballast, if that doesn't hold well nothing will! Toolstation do a 50g bottle of superglue for £2.20.
I am also in the process of replacing the plywood backboards. I have obtained some 3mm plastic foamboard from a local supplier and had it cut into eight inch wide sections. On top of this I have stuck some self adhesive backscenes. These are ID Premium backscenes by Art-Printers.com and I got mine from Expo Tools. https://www.expotools.com/cgi-bin/ss000003.pl?SO=1_3_4_0&TB=O&SS=backscene%20&PR=-1&SO=1_3_4_0&SO=1_3_4_0&SS=backscene+&SS=backscene+&PN=3
I got the 9" wide ones which are printed on polypropelene and are water and tear resistant. I suppose there may be the problem of fading with the sun over time but we'll see.