Fleet logistics after nuclear attacks on British bases

If the fleet escaped nuclear strikes on its British ports, how could its logistics be sustained?

Surviving alternative bases, particularly Gibraltar, would provide some support, but losing the main British bases would leave a major logistical problem.

The scenario assumes that ships put to sea before Russian nuclear strikes destroy their British bases. Escaping the initial attack leaves a separate logistical problem. Alternative bases would be needed, with Gibraltar identified as a remaining option if it also survives. The loss of the Scottish bases, Portsmouth and Devonport would still create a major support problem for the fleet.