The other alternative was to replace the whole bonnet but I am in no position to do that just yet.
If left in this state (pic 1) the bonnet would come off within another year. So I put 2 days aside. First I took off the hinges (remember these screws nuts and bolts have not been moved since 1970!) amazingly they came off with ease. Next job was to get rid of the rust and repair any holes. Only one 0.5cm hole needed reparing with P40. So far so good and was surprised that the rust had not penetrated the area completely judging by its initial state.
Finally the paint job. I sourced the original Almond Green from a classic car supplier rather than use an aerosol (I think that commercial aerosols are too heavy for such a small areas).
I thinned the paint myself and instead used an airbrush normally used for finer detailed work such a miniature models. Not as much masking is needed as the paint is more directional. Mine was bought from the bay for only £13.00.
The result was good/acceptable (not excellent)
however a perfect colour match 
. Now at least it is saved from corrosion for a few years to come. Bonnet saved.
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