Thanks, not too keen on digging down and building up because that then means 2 retaining walls doesn't it?

Here is a photo, hopefully it will help explain what I am talking about. Ideally I would like to dig down to retain privacy with the fence on the left as there is a park over it. The right hand side fence is dead anyway so it needs replacing.

My main concerns are the amount of digging, the possibility of clay soil and gas/electric/water pipes!