Posted: 25/11/2014 at 12:01
I think you need to remove the old soil and then dig it over (if possible) to see if there are any problems first. You might not need to put gravel down.
I do not think the compaction will get any worse now. You just need to know how it copes with any surface water. The new top soil and lawn may be enough to hold any excess water.
A sand/loam mix is ideal but a layer of well-rotted manure will help the grass and hold the moisture in the ground. Make sure it is well-rotted, as un-rotted organic matter will cause the soil surface to sink unevenly as it decays.
Once you have undone the compaction you may find that the ground is able to cope with any extra water.
Do you have flooding problems at the moment?