how do i get general dirt or filth off white-ish canvas sofa cover?

[zebramummy]

i have done several machine washes but they still look filthy. in all my ignorance i have come up with the following:

bleach them - but how, and prob not great idea as ds rubs his face on them regularly while practising his gymnastics

dylon - does this really work? same color or darker perhaps?
stronger washing machine products given that eco products have their limitations in this respect?

your opinions would be much appreciated

bump

Can't help as I have the same problem, I use vanish, washing up liquid, bio wahing powder, the works and they're still grubby. I don't bother trying to get them clean anymore, just wash them to stop them smelling bad.

maybe this is why soft furnishings courses are offered at about 10 different venues in our local area - when i saw the price of replacement covers i needed to sit down, it all started to make sense!