hi there if you were in our area it'd cost you 1250 to dash or stipple render it or 1500 to do a smooth render (labour only). personally i'd go for a multispar dash like canterbury as this gives a nice finish which has no long term maintanance and done right will out last us all. i agree with paul 3 to 1 mix but if you want the best mortar you could go with a 50/50 split yellow sand to red sand with a shovel of lime added to it aswell with the waterproofer and plasticiser, we use this mix for both coats on all family members houses so we don't have any come backs