When I extracted the baffle from the cabinet, the speaker mounting screws backed themselves out causing 'pooks' in the grille cloth when I unscrewed the speaker retaining nuts
I decided to attempt to remove the cloth which peeled away cleanly with no problems. I then wound the screws back in with a bit of Loctite.
SHMBO worked in the 'rag trade' and did some work as a conservator in the National Trust... I handed the filthy cloth over to clean. The cloth was soaked in a lukewarm plain water solution for about 20 minutes. It was then removed and placed face down on an old towel. A weak solution of Vanish stain remover and bleach was made up and the back of the cloth was patted with an old soft toothbrush dipped in the solution. This had the effect of pushing the dirt out into the old towel.
After a few rounds of dip-dabbing, the cloth was again rinsed in warm water and left to dry. I was pleased to note no shrinkage or expansion took place, and I remounted the cloth using Maplin spray glue. The end result you can see in the previous posted picture.