According to the article at the link below, the cabinet isn't plastic - it's brown Bakelite sprayed red, later also available in beige. If that is indeed so, an invisible repair is much easier as the whole cabinet once repairs, can be primed with high build primer, then resprayed the desired colour of red. There's such a wide variety of shades of red auto aerosols that an exact match should be achievable.
It will have been well towards the end of the valve radio era, having a printed circuit board:
http://www.classicwireless.co.uk/Murphy_U572.htm
Good luck with it.