I bought a new old stock set of mirrors from mini sport, rubbed them down to the plastic as I didn't know what paint was used, sprayed them with halfords plastic primer, may have put on some other primer and then top coated them with 3 or 4 layers of cellulose. This was the start of September last year, I went to fit them a couple of weeks back and they both looked like the photos, I polished them up even with the cracks and more cracks appeared since. I've rubbed them back down again and it seems like the primer has cracked as well as the top coat.
Any help so it doesn't happen again?
Cheers