larknz: My concern with using a cheap product that is exposed to the sun is that it will degrade very quickly due to the UV exposure. I would be asking about the UV stability of the product.

Most conduit is going to be buried or in walls, so UV exposure doesn't really apply there. Definitely a requirement for guttering and downpipes, and my main concern with 'cheap' brands. The one I used claims to be UV resistant, but then so do many other well-known products, most of which fall well short of what I'd expect from a 'UV resistant' product.

We see lots of PVC windows and fences going in these days. Give them a few years and the shine will be gone, leaving a rough, powdery surface, no matter what claims the manufacturer makes. Claims of colour retention are equally as farcical.