That dirty word............RUST

[FocusMP3]

Can anybody tell me what they see as a fair price to pay to have 2 complete new sills put on my 53 Plate Focus 3dr.

My car went to a body shop who originally quoted a price of 350 to treat all the rust on both sills and all 4 wheel arches, plus a few extra touch up bits.

Since then I have been told that the cars sills need replacing, fair enough I thought and he agreed to still do it for the 350 if we shelve the extra bits for the time being.

I was happy with this but since then (after he has exposed all the rust and holes in my sills) I have had no call back from him (nearly 4 weeks) to say when he wants my car back in.

I have been advised that he might be shying away from the job because it's bigger than he anticipated and he hopes I will take it somewhere else, I have handed over no money yet but my car now looks a state.

What would be a fair price to offer this guy for 2 new sills and 4 wheel arch treatments as I imagine 350 is no where near enough, I want a quality job doing and willing to pay a fair price. 

Any advice please as I am getting quite stressed over how my car is now looking.

Thanks muchly :)