When removing paint from radiators, it's important to cover and protect all surrounding areas, especially if the radiator is being stripped in situ rather than being removed.
2 paint strippers that our customers have used to good effect are Paint Panther Paint and Varnish Remover and PeelAway 7 Paint Remover. The first is a traditional gel paint stripper whilst PeelAway is a poultice or paste system.
Due to the differences in paint formulations, we always recommend doing a small test area first to establish the effectiveness of a product. Peelaway comes in a handy PeelAway 1 and 7 Sample Twin Pack whilst Barrettine Paint Panther is available in a small 250ml tin that is ideal for testing.