The rub is that the small number frigates and destroyers have always been needed for other tasks. When a carrier deploys then either these tasks are actually not needed or the carrier sails on its own.
As to how the RN will be able to muster a mixed fleet of frigates, destroyers, RFAs etc at the same time to support sequential carrier deployments remains a mystery. RN manning and RN ports are not exactly used to such events; launching vessels as and when is considerably less taxing than supporting a carrier cycle. The RN will need more money to make this capability actually work.