you can download the CSV and use some sort of conversion program or tool to make the conversion.
if you’re trying to get records into a format to import to iRecord, you might be able to adapt some Python code created by @sbushes here: https://forum.inaturalist.org/t/tool-for-exporting-inaturalist-data-to-irecord-or-elsewhere/19160.
this example uses the OSGridConverter module to make the conversion, i think, and you can also use that if you’re writing your own thing in Python to make the conversion.
if you need more help or examples, please describe why you need the OS grid references, and maybe you’ll get more help.