Oh dear, oh dear! Threre are some awfully muddled folk on this thread. As has been said earlier, at night you MUST fly under the Instrument Flight Rules (IFR) - you MUST also do this by day in Instrument Met Conditions (IMC). You may only fly under the Visual Flight Rules (VFR) in Visual Met Conditions (VMC), but in the UK, although you may be in VMC at night you MUST fly IFR.
In a control zone, and ONLY in a control zone, a pilot who cannot comply with the Instrument Rules for a control zone may be issueed with a Special VFR clearance in order to leave the zone. This will apply to Class A Control Zones at all times and other Class Zones at night.
To repeat, a Special VFR clearance can only be issued for flight in a control zone not an area, TMA, airway or any other controlled or uncontrolled airspace. There are no Special VFR rules as such - you don't even have to carry radio!