It was Bal Limestone Superflex,i ended up using Lithofin cement residue remover without any probs.
May be of interest.
Few years ago got a call from a pal who had just had a limestone fireplace that cost around £3000,individually made and fitted.
His parents had come round to baby sit and his father took a bin liner from the kitchen bin,placed it on the hearth and cleaned out the grate.When he removed the liner there was a large black oil stain around the size of a hand.Earler a pan of oil had been poured into an empty can and put into the liner.
In desperation over 1 week they tried everything-masses of water,stone etches and cleaners,rubbing stones.Bit pointless as the fat had deeply impregnated the stone.
Went round after the call and looked into any thing that may work.
Ended up trying a HG product called oil+grease stain absorber .It works by drawing up the oil.No scrubbing is involved,using a spoon i thickly dripped the liquid onto the stain till it was totaly covered,it then gradually clounds and forms a sort of hardened skin.5 hours later washed it off and all the oil had had beed drawn out leaving no slight stain what so ever.
An absolutly amazing product.
Kev