Hi Nic,
When you refit the accumulators, the oil side can be bleed at the adjacent check point on each pipe, No. 4 on your diagram. You may need to make up a little pipe to do this as it is the point where pressure checks are carried out, the cap is removed and fitting released slightly to open up. Without a pipe you might get a soaking! Obviously, this is done with engine running and there will be little air in the system.
regards, Richard