Old sandstone house - damp floor issues

Charlieepie

Just an update/ask for a bit more advice.
I’ve had some of the vinyl back in the kitchen and the floor is dry. On closer inspection (pulling back more of the carpet..) that damp bit under the carpet in the hall is localised, there’s a tide mark where it ends a little further down the floor, so we need to get it investigated but I suspect/hope it is a leaking radiator pipe into the lounge.
We’ve got a local old property expert coming to look out our house within the next few weeks but I’m hoping he doesn’t recommend a whole new floor - as there’s no evidence of damp floor or walls in the kitchen I’m quite reluctant to tear it all up.

However, I’ve just had most of the carpet back on the timber floor in the living room that needs a replacement and found that the hearth of the old fireplace is almost wet to touch! Has anyone had any experience with this? We’ve currently got a gas fire installed so there’ll still be a vent in that chimney and it won’t be totally sealed off at the top. There’s no damp patches anywhere on the chimney breast on any of the 3 floors it goes through, just the hearth is wet. The wall and skirting touching the hearth aren’t showing signs of damp either. Just the hearth. Is the fix as simple as cutting it out when we put a new floor in? It’s been under carpet and underlay anyway so not used as a hearth.