thanks nambucca i think i'll give that a go.

but...

Can i not just cover the smaller stones, after getting rid of as many as possible, with some new soil and sow the grass into that.

&

Are the birds really that much of a threat? Again, im a new gardener so im not sure on this stuff - should I/can I cover most of the seeds with the soil or do they need to sit on top?
Best time of the day to sow?
and what about squirrels?

Thanks again,
Murray