philipdayton said:DIY it is then!
You must be joking!! Have you ever worked with render? A couple of years practice might be worthwhile first.
Looking at the figures given you've got to get about 2 tonnes of dry material, mix them to the right consistency so that they stick to the wall and don't sag, then get a smooth finish on a wall that is likely to be some 16-18 foot high.
I tried using sand and cement to 'plaster' an internal wall after getting good results with lightweight carlite plasters etc. It ended up in rubble bags and I got a pro in. It is not easy even if you can use plasters (not the sticking type for cuts).
I would seriously recommend you get the job done properly, even though this is a 'DIY' forum.