In reply to Mike-W-99:
The stove was mooched from the Feshie bothy (Feshie being renovated now and new stoves being installed in there)
Bizarrely the grates which were the originals in the stove have shrunk in size, therefore the 2 rocks holding up the now wee grates.
New bigger grates being made in Perth and will be fitted in November.
The increased altitude must be responsible.