nl fairlane , power steering reservoir ran out of oil, replenished same, now the steering is heavy. Is it necessary to bleed the unit susequent to running low on oil?

yep.

I just re-filled a pump on an EB and while I had the front jacked up, turned the wheel lock to lock 6 or 7 times. That dropped the level quite a bit, about 50%.
Re-filled the reservoir, took it for a short drive including a couple of 3 point turns, re-checked the level and all's fine so far.
Cheers,
Paul