Exrigger, whereas that it is true for the Vulcan B2, the B1 and B1A had totally different electrical systems. They also had ailerons and elevators rather than the elevons of the B2; however electro-hydraulic PFCUs were indeed fitted to all Vulcans.
The B1 and B1A had a basic 112v DC electrical system, with 4 x 24v batteries in series for back-up power; any AC needs were provided by inverters and transformers. There was also a low voltage 24v DC system with its own back-up battery. Whereas the B2 had a predominantly 200v 400Hz AC system, which was a vast improvement.
In the B2, if all 4 engines flamed out (e.g. after the shock front from a high level nuclear burst had been encountered), there was a RAT which would provide sufficient power at high levels to maintain flying controls whilst relighting was attempted; this was augmented by the 'Rover' AAPP at lower levels. The RAT/AAPP drill was a frequent training requirement and worked fine provided that no-one was stupid enough to allow an over-volting RAT onto the synch busbar. (Spilsby....??)
Although the B1 had the 4 x 24v 40Ah back-up battery system which was supposed to provide sufficient 'get it down' electrical power if the main electrical system failed, in the case to which Fonsini refers, the battery gave up long before it should have done.