Best way to clean sofa upholstery?

[Sinkingfeeling]

I've just bought a great sofa from a charity shop, and it's generally in very good condition, apart from some dark marks on the sofa arms, where arm covers would normally be. What's the best way to clean them? I think the fabric's a cotton/linen blend.

I need to attack the arms of my Laura ashley armchair, so watching with interest.

When I hire the rug doctor for the carpets I normally do the sofa's aswell, that normally brings them up nicely...

If you don't want to do that may be a vanish upholstery cleaner?