Your chimney sweep can supply and fit cut to size replacement fire bricks. (flat brick only)
The firebricks in a stove reflect heat back into the fire which allows for a hotter, cleaner burn but these are wear items and will need replacement from time to time.
If a brick is well supported on three edges then it can remain in place.
As a general rule a single hairline crack is not a problem.
Replace if it looks like it could fall into the fire.
Replace if you can see the stove wall behind.
We can fit replacement firebricks, supplied by you, free of charge, after sweeping.
Wood burning - sweep every 3 months in use.
Smokeless - sweep every year.
Coal - Never burn coal in a stove with a liner.