To reach the canal towpath with a bicycle, cross the bridge and follow the track to the left to the lock. There you can cross the upper lock gate to access the towpath towards Brighouse.

Not sure if I've already flagged this up but I saw no trace of a path across this field - marked 'private' - to the river. I also suspect the 'river path' here may be almost non-existent.
Everyone heading to or from Brighouse leaves/joins the waterside path at the stone bridge by the second lock.
I recently added a path, leading to the lock on the far side of that bridge, that makes getting a bicycle onto/off the towpath a lot easier.

The hotel no longer exists. It has been a private residence for about two years now.

Warehouse Hill Road stops at the bridge over the Huddersfield Narrow Canal, at which point it becomes Marsden Lane.

Whitestone Lane is no longer a through route for vehicles. You cannot use it to drive from Bradford Road to Alder Street.