I know I'm heinously late on this this one, but get down to Halfords and buy a big 1L bottle of Dot4 Clutch & Brake Fluid.
It's not too expensive, it is reusable, and it hasn't really got any terrible odours or anything. As far as I can tell, it is basically mineral oil. That means it is a bit harsh on your skin if you scrub the minis without rubber gloves (it will dry your hands out like White Spirit does), but not much more. You can strip anything in it (metal or plastic) and it will have no ill effect on the model.
I keep the stuff in glass jam jars and just fish the parts out after a week or so for vigorous scrubbing with an old toothbrush and some Fairy detergent - you will need some plastic dental picks too; as the paint goes puffy, soft and stretchy, it tends to get stuck in the deeper recesses and needs to be picked out.
Now, the things I've stripped have been painted with GW paints and sprays for the most part (as far as I can tell!). The models may need two or even three soaks, but otherwise even GW Chaos Black spray comes off if you bathe the victims long enough! No idea if this works on enamels though.
As for how long you can soak your plastics in the stuff... Well I've had some old Adeptus Titanicus Titans and other Epic plastics in there for about a year now, and so far no ill-effects (the models were crusted with very old paint; hence the long soak!).