Keygrip,
He can't fly IFR, because he's flying in France, and his ICM rating isn't valid there! However, your link does provide the answers.
Keef,
In the document which Keygrip links to, on page 191 is Schedule 8, Part A - Licenses, 1 - Aeroplane Pilots, Private Pilot's License (Aeroplanes), c:
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:
...
(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 sub-paragraph;
Since you have an IMC rating, we also need to refer to page 208, Schedule 8, Part B - Ratings:
Instrument meteorological conditions rating (aeroplanes) shall within the United Kingdom:
.....entitle.......
(c) the holder shall not fly:
(i) on a special VFR flight in a control zone in a flight visibility of less than 3 km;
Since you are not "within the United Kingdom", this does not apply. So my interpretation is that you must have 10km vis in the situation you describe.
Have fun!
FFF
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