OK. The picture is more in order now. The picture has the Up and Down properly aligned.
I tried to apply the logic of the CR Platform 1b having persisted and removed facing points from the Branch passenger approach to it, reasoning that if the CR needed to gain access, it could come onto the Up. I added a bracket at the entrance to 1b, with calling on and a subsidiary arm for the RR loop. I made the assumption that this "special" signal being squeezed into the train shed was one that the LMS chose not to replace along with its 1b starter cousin. I also added a main and call-on for Pl1a to 1b, presumably hanging from the rafters! The platform 1b starter has a bracket with an added calling on arm on the Pl1 side, I presume to allow movements to unify a 1a and 1b train. In fact that seems quite an operationally attractive idea, a train is bought into 1b and its carriages are added to a train standing in 1a, or a 4/5 coach train is brought into 1a+1b and divided into two. "the two front coaches on this train are for Pwhelli, the rear portion is for Nantlle"
I assumed that there is a GF for the 1b engine release. Hints on signaling this whole section would be welcome.
The new throat adds extra distance such that the gantry is now "one-way" in front of the left hand road bridge and only has arms for the exit roads outbound. In each case there is a branch and up signal pair and a smaller arm for access to the down to shunt except for the branch which has no access to the up. I assume this branch pass arm could be dispensed with actually. All branch pass clearances either way would lock out the signals that would allow access from the branch to the Up and the crossovers between up and Goods.
The lack of access from the branch passenger to the goods facilities means that they are reached by plain crossovers from the up. There is a crossover from down to up just before the double slip pair to the branch that could have been combined with the line from the Gds In to Down, but having them separate gives positions on the Up and Down where a loco (e.g., pilot) can wait before being called on, or with a few wagons during run-round of the goods train in the Gds In side without fouling the other lines.
I removed the Pl4 arrangement as "70s" and left it as a ground frame and some simple ground signal signaling to protect shunting movements in Gds Out.
The lever numbers shown are all "nominal" right now.
Question - how would token exchange work on the branch? While there was a box at the end of the single track, it was easy. Now with a large semi-automated (pneumatic) box on the other side of the tracks - how would that function be done, or would the old box be retained for that and have control over the branch signaling up until the station throat? In model terms, this gives the possibility of something else for the person operating the goods yard, WR Shed and Gds Yard to do!