Yes, cutting power to an AC unit at the fused spur or plug socket is safe to do so. From Senior Electrical Engineer at Syska Hennessey: 'Switching the power on and off does the same thing as what would happen when the motor controller turns the compressor on or off. In either case, you will have a transient surge current when the motor starts. The rotor in the compressor motor needs to overcome inertia in order to start turning from a stationary position. This requires a starting current that can be as high as six times the normal operating current, depending on the type of starter. Reduced voltage type starters can reduce the starting current significantly'.
Generally, it is recommended to avoid frequent on/off cycling of your air conditioning unit within very short time intervals. Try to wait at least 5-10 minutes before turning it back on to allow the system to properly reset and avoid potential issues with delayed cooling, increased energy usage, and wear and tear on the system.
In terms of the energy savings from turning off AC units for hours overnight, at weekends and during holidays. The savings in energy consumption, cost and emissions far outweigh any startup power draw.