AJ 24.02.22: RetrofitThe retrofit issue features three building studies: Btzow Brewery in Berlin by David Chipperfield Architects, Rugby Radio Station's transformation into a school by van Heyningen and Haward and St Paul's Cathedral School by Kilburn Nightingale. Will Ing visits Central Hill estate in London to meet residents who are challenging architects not to demolish it. In a separate news feature we speak to Annabelle Selldorf about the makeover she is planning for