SteveO wrote:
The turf as it is, isnt very good. What i really need to know is
what
to fill the void with, is there something i should use under the
topsoil, that also may be cheaper.
[...]

Hmm. You could lay six inches of crusher run aggregate -- in size
about four inches down -- and then import your new topsoil onto that,
which would improve drainage and be cheaper than topsoil all the way.
But I'm not sure how much money that would save when the separate
costs of transport came in: find out the delivered cost of each, and
calculate from there.

But I know I'd leave it as it is, since I think you're very lucky to
have a garden on more than one level. Have you considered the fences
or hedges? If you don't build a strong low wall, they're going to
have their bottom eight to fifteen inches submerged in soil. This
will kill some or all of any hedge, rot or break a wooden fence, and
give you a new view into next-door's garden -- you could stand on a
box to see how you and they like it. And soil will spill through the
old hedge or rotting fences into those gardens next door: I don't
know how welcome that will be!

--
Mike.