How can I get this looking clean?

[Sortoutthehouse]

We have some lovely pieces of stonework in our house but a couple of the pieces are looking a real mess, I've been in the blur of young children / busy job and now finally feel like I have the time and motivation to sort our old house out and get it feeling more homely (and deeply rather than surface level clean!), how do I go about cleaning this -I've tried just scrubbing to no avail. What product do I need?

Photo helps obviously, hope this works!

Anyone?

Is it sandstone or limestone? A bit hard to tell from photo.
Many stones need an acid based cleaner. You will be able to find products online once you know what the stone is. HG products are generally good quality

Thank you mumaway, I have no idea but will look into this and look at the hg brand. I really needed a starting point