Today I had a good look and discovered that the two small holes had indeed gone through...so I stuck my hand in the void inside and discovered sopping wet insulation. I have removed all the wet stuff and dried and vactaned from the front and back, now Im left with two small holes. No other rust or holes in that area.
Whats the best way to fill ? Filler or spot weld or some other way I don't know ?

Many thanks