Hi SpaceBadger,
that's what ICAO says:
ICAO Doc 4444 6.5.3.3
An IFR flight may be cleared to execute a visual approach provided the pilot can maintain visual reference to terrain and:
a) the reported ceiling is at or above the approved initial approach level for the aircraft so cleared; or
b) the pilot reports at the initial approach level or at any time during the instrument approach procedure that the meterological conditions are such that with reasonable assurance a visual approach and landing can be completed
Executing a visual approach does not mean you are not an IFR flight anymore. Separation has to be applied accordingly and as far as I know you are charged the full IFR approach fee.
Regards
DG