Hi
Hooksey and
BB,My congrats also doing all the hard work yourself. It looks great, and will be brilliant when the lawn establishes.

I must admit I agree with BB on the problem of termites...Here is an excerpt from a well known pest extermination site in WA....
"And ideally the area around the house should be paved and garden beds adjacent to the house removed. Railway sleepers make great termite nests as well as old stumps and dead trees, so we recommend their removal as well."
Knowing only too well the extreme damage that termites can cause...plus the fact that you
can't insure against the damage....(they can structurally damage a family home in just months) I would seriously consider removal of the sleepers....Forewarned is forearmed, the choice is up to you, mate.