Seeing as storm Kathleen is either trying to wash us away, or blow us away, I finished off the hammerite and did a dry brush of the radiator before trying the simple green. Its still pretty blocked even though its not that long since it was in the dish washer
Oh and accidentally bought another radiator which was allegedly the last new one at bmw sycamore. Haven't seen any new ones elsewhere recently although I haven't searched exhaustively. Still, would rather be looking at it than looking for it.