So having an IMC removes a restriction on your plain vanilla PPL, and that means that that restriction is also no longer present when flying on your 61.75 FAA PPL.
That depends on which licence you hold. It is indeed true for a JAA licence, but not for a UK licence where Para 2 c (iii) out of sight of the surface is limited to the UK. ANO Schedule 7
(1) Subject to paragraph (2), within the United Kingdom an instrument meteorological
conditions rating (aeroplanes) rating entitles:
(a) the holder of a United Kingdom Private Pilot's Licence (Aeroplanes) or a United Kingdom Basic Commercial Pilot's Licence (Aeroplanes) to fly as pilot in command of an aeroplane without being subject to the restrictions contained respectively in paragraph (2)(c) or (f) of the privileges of the United Kingdom Private Pilot's Licence (Aeroplanes)
(2) The holder may not:
(c) unless the 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 if the flight visibility is less than
three 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 sub-paragraph; or
(iii) out of sight of the surface;