For instance, I know that I need 10km of vis for an SVFR into a Control Area, rather than perhaps knowing what I don't need.
2 errors in that statement; you need to find an up-to-date source of information!
SERA.5010 refers to Special VFR in control
zones:
Special VFR flights may be authorised to operate within a control zone, subject to an ATC clearance. Except when permitted by the competent authority for helicopters in special cases such as medical flights, search and rescue operations and fire-fighting, the following additional conditions shall be applied:
(a) by the pilot:
(1) clear of cloud and with the surface in sight;
(2) the flight visibility is not less than 1500 m or, for helicopters, not less than 800 m;
(3) at speed of 140 kts IAS or less to give adequate opportunity to observe other traffic and any obstacles in time to avoid a collision; and
(b) by ATC:
(1) during day only, unless otherwise permitted by the competent authority;
(2) the ground visibility is not less than 1500 m or, for helicopters, not less than 800 m;
(3) the ceiling is not less than 180 m (600 ft).
There are no longer any additional, more restrictive limits for NPPL / LAPL holders or PPL holders without instrument qualifications.