As said plastic glue is gonna be tough, as its supposed to weld the parts together, Cutting them apart might be the only way.
If you used superglue, then cold is the trick, freeze the parts and they usually fall apart by themselves.
If you used citadel plastic glue, your in luck as that stuff is garbage; just drop them into some of your fav paint stripper... mine is isopropyl alcohol 99%. dettol liquid, simple green, fairy powerspray(dawn power dissolver), oven cleaners, brake fluids, degreasers... endless suggestions goin all with pros and cons

Most of these will also severely weaken
GW plastic glue to the point that its just a little bit tacky and can be pulled or pried apart easily (At least in my experience)