As a temporary fix, I filled the holes with chemical metal (more successfully than I had guessed 

 and repainted it all.
			
		
				
			 
- RoverAirFilter.jpg (23.57 KiB) Viewed 37793 times
 .
I read that in use it gets oil 
vapour from the engine.  But how should I first fill/inject it with some oil?
Would 'Duck Oil' from an aerosol can (with the thin pipe/nozzel)  be any good?