Sandstone house repairs

Hi. We live in a late Victorian sandstone house near the sea. Over the years (and prior to us owning the property) various repairs have been done using cement - which turns out to be a big no-no, and in addition, there is a large crack in the vertical stone bit in the bay window. We've had three supposed "stone masonry" companies out to look, but each have told us different things and suggested different course of repairs, from various chemical stuff to grinding back the whole front wall by a couple of cm to get to fresh stone - which seems awfully drastic to me. I've googled loads, but since I don't know a lot, I'm not sure what's legit advice and what's baloney. Can anyone direct me to a reliable source of advice on this?