Out of interest, are HS1 signallers (And the Ashford control centre) separate from NR?
No, NR are contracted by HS1 to provide signalling and electrical control, and do so from the operating floor of Ashford IECC.
My guess is Pwllheli.
No idea.
But I'll take a shot with either Aberystwyth or Pwllheli depending on exact Cambrian implementation dates.
EDIT
I see someone else already answered.
Aberystwth.