Giles,
Your layout is superb, both visually and in operation. However if I could just make one slight comment regarding the grass, which is outstanding and much the best way of applying static grass but I think there's possibly just a little too much of it especially round some areas of the track. Considering the operation as in your video of the prototype system, without the benefit of automatic coupling/uncoupling and points which change by magic, the driver would be on and off the loco several times to uncouple, change the points, re-couple, etc, walking regularly between where the loco stops and the operation required, and these areas would be largely free of grass and well compacted. If the driver had an assistant, usually a young lad would be normal, he would tend to walk between each operation rather than jump on and off the loco, so a greater area would be regularly walked on. Remember the old saying (or maybe its something I've just made up ?) - "grass grows where nobody goes".