Firstly, I bought a metre of aluminium strip, 20mm wide x 2mm from B&Q (here in UK) for £5.50.
Next job was to cut and bend it into a wide U shape to fit exactly the dimensions of the lid.
I then glued it in place before drilling holes from the inside where the screws originally went through the plastic.
The original screws are too short as my repair needs to go through the aluminium and the plastic into the metal hinge. I used 3/16" countersunk machine screws, about 1/2" long should be ok.
The good thing about this repair is that the plastic is sandwiched in between two metal surfaces so should last forever.
As a finishing touch, carefully remove the original aluminium foil strip bearing the B&O logo and reapply it to the top using double sided tape.
I managed this repair first attempt after a bit of cussing and swearing trying to get the screws to align properly with the hinges. I did buy a spare strip of aluminium in case I made a pigs ear of it, but I'm pretty pleased with it, and it is in keeping with the look of the original.