Hi David,
Only just catching up with this post, really excellent work.
Not sure if this has already been discussed or whether you have omitted it but there is another road to the side of the service shed (aka "greenhouse"), the road runs all the way down the side of where you have 3 points already now, theres then a set of points that allows locos to either enter the greenhouse or park up to the side.
Locos would arrive down this road and stand until they could be dropped in for servicing.
cheers