Thanks for the replies, folks. My understanding is now:
No IMC: SVFR (except in class A zones) is basically no use, as the vis minima are higher(!!) than for normal VFR; the only advantage would be avoiding the 1500 ft clearance over towns rule.
IMC / IR: You can use the reduced minima of 3000m / 1500m depending on which rating you have, if you don't want to bother going under IFR.
Now if only the good old JAA exams taught air law as it exists in our country, not as it exists in the idealised, non-existent ICAO land!