Thank you Charles, I have looked up slug and ants eggs on Google (sorry I should have done that first) and my flecks are definitely not either of these. Mine look like corse talcum powder, raw semolina or raw ground rice. They are a fraction of a mm, I would say a 1/10mm. The compost is riddled with them.I would be grateful if anyone can help me identify them and suggest whether or not the compost is useable.
Thanks