On the radiators, a dip tank stripping company might be the best solution..Check the phone book for furniture refinishers and call a couple to see if they have a tank and get prices. If you can't find any, call a couple antique stores and see if you can get them to tell you who they use.
On the doors, particularly if they are panel doors, I think that makes a better DIY project and will leave the old patina on the wood that the sander will take off and it will not dry out the wood the way tank stripping will. Depending on the amount and age of the paint involved, I would start with Citristrip. Follow their directions and if you have questions they have a web site. If the paint is really thick, I would use Peel Away, available at specialty woodworking stores and mailorder at such places as Woodcraft and also available at some home centers. With this, you paint on a thick coat and cover with their special paper to let the chemical work for a day or so, then peel away the old paint. If residue remains, then get it with the Citristrip. I find that washing with Citristrip Paint Remover Wash really inproves the job. Follow the manufacturers instructions and safety precautions. These are about the safest products that will do the job but you can still get injured. Henry