Replacing sandstone around window?

[WhyHasAllTheRumGone]

DM has a bay window which is bordered with sandstone. On the left hand side the sandstone has weathered badly and is in need of replacement. A builder has suggested replacing with concrete which will look the same as the stone once painting. DM wanted to check out the relative prices of the sandstone or concrete replacements but we don't know what the piece is called? It's it still a lintel if the piece is vertical?

Any information or advice appreciated.

We had outs replaced in our old house and I can't for the life of me remember.
We went for sandstone from a stone Mason FWIW as was advised that the texture with concrete might be different to the remaining stonework.

Thanks ohi. About how much did it cost?

Anything other than a matching material will show in time. these seem cheap enough to replace the whole lot, then you will have a match. Sandstone would appear to be several hundred pounds.