Thanks for all the great ideas everyone and sorry I didn't explain the polycarbonate a bit better :) This is along the lines of what we'll be using... http://www.psp.co.nz/building-brands/corrugated-sheeting/suntuf-polycarbonate The area is an absolute sun trap and we're hoping to use it as an extension to our living space, especially on rainy days! I've just sent my husband out to get a few pots of different stains for is to try - darkest brown (cedar) and a lighter brown (rustic oak) both by Cabots + the black we already have. Hopefully we can decide between one of those! I probably should have mentioned we will have black aluminium pool fencing running along the top of the second retaining wall - so the real question is do we keep everything black (pool fencing, horizontal fence, retaining walls and pergola) or do we go with a dark (or even light) brown for the pergola and retaining walls.... We just keep going around in circles at the moment. Decisions, decisions! Thanks again :)

Looks like the palm tree look is working so I would blend that with some succulents maybe agave which can grow large and make great statement plants. Also stick with the stones.

A tiled courtyard, exposed to sun and weather and under-utilised is transformed into a stylish and friendly space with the addition of a louvered pergola structure, feature stone wall, custom made wooden furniture and new tropical plantings.

Is the photo the right way up ? It looks like it would run off at that angle . But if it is building up , and draining isn't suitable , then a flashing sealed would be the logical thing , or possibly something like 30 x 30 battening ( treated and painted ) a few cm out to deflect the majority of any water .