Cross Check: 747-400.
Hymie:
Ours are all GEs, so I can't address the RR installation. Also, our FHB does not tell me what bus the demand pumps are on. I don't know if they are included in the "various flight control components" powered by the Main Standby Bus or one of the battery busses.
Normally, the demand pumps are not running with the flaps up and normal hydraulic pressure available from the engine-driven pumps. We do not practice 0-engine procedures in the sim, so I can't vouch for hydraulic pressure at windmill speeds (the demand pumps would compensate during any single- or 2-engine failure). I expect, however, that the engine-driven pumps would provide adequate pressure for flight controls at 220-240 KIAS, but would probably bog down on gear or flap extension.