Escape Path
we've done FCU 1+2 fault on the sim, which leads to flying with the Stby/ISIS due to loss of baro ref (it goes to std).
That is not the way to handle the problem. You have PFD with altimeter stuck on standard. Set ISIS altimeter to QNH. Either note the difference and fly normally with PFD or only use ISIS altitude. Don't throw the baby with bath water.