Hi Calum, nice/interesting to see the progress pictures. Looks like the finish of the various pieces has improved too from when I build mine.
That valve block sure looks impressive!
Note - I know the upper rollers are just installed temporarily (pictures posted )9/23), but be aware that the shorter end is supposed to be to the outside. In the pictures you have them alternating. That way your track will not track.
Here a picture of what I mean: