Thanks a lot for all your answers! Much appreciated and very enlightening.
I just wanted to come back to sapperkenno and MartinCh comments about day-VFR limitation.
Here is what I read in the
ANO Part 6 Art 62 (my bold):
Deeming a non-United Kingdom flight crew licence and any Part-FCL licence valid for non-EASA aircraft and deeming a non-United Kingdom radiotelephony licence valid for any aircraft
62.—(1) Subject to paragraph (2), this article applies to any licence which authorises the holder to act as a member of the flight crew of an aircraft and is—
(a)granted under the law of a Contracting State other than the United Kingdom but which is not a Part-FCL licence;
(b)granted under the law of a relevant overseas territory; or
(c)a Part-FCL licence.
(2) This article does not apply to such a licence if it authorises the holder to act as a student pilot only.
(3) Subject to paragraph (6), for the purposes of this Part, a licence to which this article applies is, unless the CAA gives a direction to the contrary, deemed to be a licence rendered valid under this Order.
(4) Subject to paragraph (5), the privileges of a licence deemed valid under paragraph (3) are restricted so that it does not entitle the holder—
(a)to act as a member of the flight crew of any aircraft flying for the purpose of commercial air transport, public transport or aerial work or on any flight for which the holder receives remuneration for services as a member of the flight crew; or
(b)to act as pilot of any aircraft flying in controlled airspace in circumstances requiring compliance with the Instrument Flight Rules or to give any instruction in flying.
(5) The restrictions in paragraph (4) do not apply to a flight radiotelephony operator’s licence or a Part-FCL licence.
(6) A Part-FCL licence with single-engine piston aeroplane privileges is not deemed to be rendered valid for a microlight aeroplane unless the holder of the licence has undergone differences training in accordance with Section 2 of Part B of Schedule 7, appropriate for a microlight aeroplane class rating.”.
Until recently, night flying in the UK implied IFR, so this effectively restricted the privileges of ICAO licenses to day-VFR.
Now, since the implementation of the information notice
IN–2012/145: Introduction of Visual Flight Rules (VFR) at Night in the UK on 17-Sep-12, I am not sure the day-only limitation for an FAA license holder (i.e. with night privileges embedded in the license) still holds.