Coopervane
There are no grey areas - from the ANO, Sched 8, part 1 section "Privilieges of the Private Pilots Licence"
He shall not, unless his licence includes an instrument rating (aeroplane) or an
instrument meteorological conditions rating (aeroplanes), fly as pilot in command
of such an aeroplane:
(i) on a flight outside controlled airspace when the flight visibility is less than
3 km;
(ii) on a special VFR flight in a control zone in a flight visibility of less than 10
km except on a route or in an aerodrome traffic zone notified for the
purpose of this subparagraph; or
(iii) out of sight of the surface.
Now, as for flying on top - you have to ask yourself the question "How much cloud, as a PPL holder with no additional ratings, can allow you to do this?" It's very much up to the individual - the wording above is quite specific. However. as a rule of thumb before I got my Instrument qualifications I used to say FEW or SCT (1-4/8's cover) cloud was fine - BKN was a definite
no as it can become OVC very quickly!
