With the use of a jigsaw and dremel I gradually trimmed the grill away until I was left with the rectangle frame.
I then test-fitted the indicator lamps to check that I had cut the right amount of plastic out.
The mesh I used was diamond mesh 100cm x 30cm, purchased from an ebay seller IIRC.
Cut to size with a pair of clippers and test-fit into the grill with the indicators too.
To tidy up the raw edge I bought a strip of U channel in which I cut mitred angles with a craft knife to fit to the grill without gaps.
The grill surround was now ready to paint so I also masked up the indicator lamps to paint 2/3rd of them - this still allowed for plenty of light to shine through the top third.
After the usual process of gradual wet and dry sanding and building up layers of primer.
And the top coats and lacquer.