there seems to be 2 levels of quality from China
I'd say four levels Barrie. There's the odd ones like Wisper and Ezee who are led by dedicated people and build their bikes to a high standard, constantly trying to improve them and listening to their customers. They also back their products with top ranking service.
Then there's a mid-budget mainstream where the bikes are built of basic but sound components but remain consistent, and these are usually imported by companies who wish to stay in the business and do their best to give good service with resources perhaps a little more limited. To give just one example out of a number, Juicybike are typical.
There's a small group below that which are basically sound bikes though often using older technologies, but imported in bulk and sold at rock bottom margins and very low prices. The Cyclamatic bikes sold by SportsUK are typical of this group.
And then there's the junk, constantly changing models and specs, sold online through ebay etc by manufacturers and importers just out for the quick buck. These aren't necessarily low priced either, they are often at high prices and sold with inflated specs to trap the unwary.