This is an excerpt from the CAA's "Guide to Visual Flight Rules in the UK", which does not really address the exam question, but does explain what to do if there is no reply:
Availability of the MATZ Penetration Service
A MATZ penetration service will be available during the published hours of watch of the respective units. However, as many units are often
open for flying outside normal operating hours, pilots should call for the penetration service irrespective of the hours of watch published. If,
outside normal operating hours, no reply is received after two consecutive calls, pilots are advised to proceed with caution. Information on
the operation of aerodromes outside their normal operating hours may be obtained by telephone from the appropriate Military Air Traffic
Control Centre