Shawn: we fly utilising "Visual Contact Flight" under our UK PAOM:
[CAP 612].
Visual Contact Flight (VCF):
A flt in which the crew is in continuous visual contact with the surface. The crew shal be able to (by day) assess a/c attitude and separation from the surface by external references.
By night, to assess a/c attitude by ref to a clearly distinguishable external horizon provided by natural lighting or artificial lights spread deeply and widely across track.
To be regarded as being clear of cloud for the purpose of maintaining VCF below 3000' AMSL, a helo shall remain atleast 50' below the c/b by day and 100' by night.
It then goes on to describe performance criteria blah, blah.
TC