In Ireland you require a minimum of 500ft cloud base.
At an aerodrome within a control zone, special VFR flights shall not be authorised to land,, take off,
depart, cross the control zone or operate locally therein if the ground visibility within the control zone is
less than 1500m and/or the reported cloud ceiling is less than 500 feet, except in the case of a helicopter
operating in accordance with Rule 3(2)(b) of these rules, along a prescribed route or within a prescribed
area where lower limits are prescribed.
Enr 1.2 for the rules.