Canny - I would recommend digging the soil away from the base of the wall allowing the render to continue below the finished garden level, looks much neater on the finished job.
Good luck!
Sconhome
Advice much appreciated and will definitely follow this advice, had a look at a neighbours newly plastered wall after reading this and you can see very uneven finish above the grassline where the plaster ends at the base.
Also thanks to everyone else for their helpful comments and advice.
Thought I would let you all know that garden is now finished. Garden walls look fab - plasterer did a great job and earned every penny (final cost was 850 euro). He also advised capping walls for a better longterm finish and my neighbours are going to do the same and share the cost so we are all happy!