Do it yourself. Surley it neednt be a professional job in the garden. Make a feature out of the 'swishes' you are likely to leave. Or roughcast it with pebble dash for a rustic look. The approx €2k you will save can be used to invest or spend as you feel. Plasterers can charge what they like. They are skilled, most, and are best off getting well paid for interior work. Of course if you want to pay it, or even half this, do so. If you do you are indicating good value for you for the job done.