Isopropyl alcohol works .
It doesnt damage the plastic and is the same as the Tamiya brand acrylic paint thinners.
This stuff also works on Citadel Miniatures spray cans and will strip Vallejo acrylics.
Be prepared for a lot of rubbing.
It will also shift cured paint (acrylic) so if you want to strip an old kit for a fresh paint job its your best shot.
And its relatively cheap at €8 for a litre in any pharmacy.