Thank you all for your comments. Well, it's been a few months since my original post and we have since finished putting up the retaining wall and planting the hedge. We decided to go ahead with Murrayas - planted about 34-40 cm apart. I gave them a good trim about a week after planting at the end of Autumn and another quick trim at the start of Spring. They have really filled out in warm weather and I think the gaps between individual plants should close by the start of winter. I'm really happy with the choice - the hedge looks glossy and lush and the sweet smell of Murraya flowers is just beautiful. We didn't do any underplanting, but I'm still thinking about putting in the dwarf agapanthus for the inside border. A couple of weeks ago we planted some Rhaphiolepis "Snow Maiden" and Rhoeo along one side of the retaining wall to provide a border for a footpath and I'm really happy how it turned out.

How beautiful, could be a sweet viburnum, take a piece to your local nursery for identification, looks very hardy, if it is viburnum then it needs a trim to keep its shape, a slow release fertiliser and it likes to be kept in moist well drained soil. Looks like it is well established so it will be easy to maintain , how lucky you are.

I would use viburnum as they are a great hardy plant, there is the sweet viburnum , or emerald lustre or dense fence, lovely lush foliage and white flowers, need a good free draining soil and to be watered regularly, you can grow them to whatever height you like, they respond beautifully to clipping and enjoy all weathers , a slow release fertiliser during spring keeps them looking beautiful.

Hi Kylie, look at OzBreed varieties 'Quick Fence' and 'Dense Fence'. They're stocked by a few different places, the OzBreed site will advise where they're stocked too. Best of luck! I'm also considering the same varieties at the moment