According to AIP, ATC can only authorise a visual approach when, amongst other things:
receiving an ATS surveillance service, the flight has
been assigned the MVA and given heading or tracking
instructions to intercept final or to position the aircraft
within the circling area of the aerodrome.
If they aren't doing that, ask them to.
My experience has been that in radar coverage, ATC will progressively assign lower levels until the "ESTABLISHED ON OR ABOVE PAPI, CLEARED VISUAL APPROACH" call, or in non-radar, "DESCEND NOT BELOW THE DME/GPS STEPS, CLEARED VISUAL APPROACH" or similar. Sometimes they need a nudge (as we all do), but just do what you're told, and as already pointed out, you can't descend below your last assigned level except in accordance with the AIP.