Lime/bath stone - In need of clean and repair
I have no experience of cleaning this stone, but I do recommend caution using any products you might find yourself.
Cleaning this type of stone is a likely to be specialist job, especially on a historic building. There is a risk of damaging the face of the stone and any work you carry out might be restricted by local regulations for listed buildings, conservation areas etc.
https://beta.bathnes.gov.uk/sites/default/files/2020-01/clean_bath_stone_0.pdf
https://borealabode.com/bath-stone-cleaning-repair