Three year update.
Since I can only buy cheap eBay wrap locally, my wraps haven't faired particularly well. They're only supposed to last 5 years max so I guess I haven't done too badly. I imagine, the 'max' is only going to happen on a garaged car and when applied to a vertical surface.
Here you can see the results. On the left I've removed the panel, and you can see it's all shiny and chromey underneath. On the right the panel is still mounted. In between is where the wrap has turned white and started to crack and peel.
Good news is the wrap did it's primary job of keeping the roof paint protected, even with some cracks letting water in. Still a fair old hastle to remove the degraded old wrap.
The Proton didn't fair as well:
At first the shadow chrome started to turn a pretty cool rust effect, I was OK with that.
Eventually, it turned matt black (the hottest colour of all) and started to crack. On removal, the wrap adhesive had
fused to the clear coat and damaged the roof. This car was kept out doors under a tree so it only got morning sun.
The wrap on the Jeep is also gone, there was no way it would stick to the textured surface. Even duct taping the edges meant that the low pressure zone at the middle/rear of the roof would balloon up at speed.