Glowworm Spacesaver 50 BF sooty?

My faithful Boiler of 25 years is producing soot despite cleaning. It has been suggested that the burner unit is at fault as everything else appears OK . I have been told this is no longer available and my boiler will be condemmed because of this which is a crying shame.

Can anyone advise if this part can be acquired or if my existing one can be cleaned/ reconditioned.

Desperate as I have no heat but more urgent no hot water.

I have heard and seen so many horror stories about the newer combo boilers!!!!!!!!!