I had a similar situation. Part of my fence is slat & & part is cap & lap. To cat proof it we put silver grey polycarb on the top half & i painted the slat to watch at the front. I was going to paint the cap & lap but as my builder pointed out, it will silver with age & the plants will grow up to hide a lot of it plus once you paint it has to be repainted every 8 to 10 years not to mention the expense. It is bugging me to look at this half pine wood half polycarb fence until it silvers but he makes a good point. I guess it comes down to money & what you can live with.

With the deck being quite narrow have you considered taking the timber to the edge of the deck and not using a coping stone. This will give you a sleeker more clean lined look. With regard 90 verses 140 decking. We use mainly 140mm now, but with the deck only being 2 metres wide this may look out of place. A lot will depend on your surroundings. If the deck hasn't been started yet I would also suggest that you run your decking the short length, this will draw your eye along the lines and give an illusion of the deck being wider than it is and looking up it not as long. With regard cupping it very much depends on the timber selected and you really need to screw down rather than nail. For almost all of our decking I specify and recommend Accoya for its stability. I am sure that it will be available in Australia.

With a million variations through a million computer screens you will get a million suggestions and very confused while no closer to your answer. You have to do the work yourself and either get a colour match to a chip the min of a 50c piece or buy a Dulux or Taubmans fan deck and select a colour as close as you can. Alternately get a professional painter or decorator to use their fan deck or atlas to colour match for you and be prepared to pay them for their time.

Thanks for the suggestions. I knew the brains trust would offer good options. Blue board looks interesting. I need whatever I use to be at least 15mm thick so that there aren't any toehold edges between the lattice and the surround frame. Yes we thought of painting the fence and perhaps contrast bamboo in front. Mini orb I don't think would work because the corrugations leave gaps between it and the lattice.