Bartoline TX10 from B&M or other outlets
Bartoline TX10 Paint & Varnish Stripper. A highly effective water based formulation, which is non flammable and biodegradable. Size: 500ml (Approx.)
www.bmstores.co.uk
Got this to take enamel paint of a white metal kit, It did the job so can cope with the paint. Wile doing so I thought to try it on plastic, was ok, In fact it did not even touch the Acetate glazing on the White metal kit that I left on as was just going to use new. Longer testing showed that it was over a week before plastic started to suffer by going soft.
My method was to pour in a tray and put the model into it, then turn to a new surface after about an hour, once all done, wash off with water and an old tooth brush.