I think you're nearly there... Select one part in the schematic. Click on the package attribute to open the Footprint Manager. Search and select the new package in the right hand search panel. Then, in the left hand component list column, filter and then do left-click on the first in the list and Shift-left-click on the last to select all the filtered parts. Then click Update. Then click **Update**. Then do **Update PCB.../Import Changes...**

Thanks - worked once I selected the diodes in the left first, THEN reselected the package.   Also the double Update seems to be needed as you say but no idea why. Thanks for your help

The first Update, updates the package assignments of the symbols in the schematic. The second one pulls the new packages into the PCB.