Apart from freight charges there's VAT and duty - both fixed and based on the invoice value of the goods you bought. If you are thinking of a FCL (full container load), you will have to account for transport from dock to your location, insurance, import documentation & port fees, unloading costs, storage costs.
Chinese manufacturers/exporters will usely ask for approx 40% of the invoice value in advance, and then the remainder when they submit the container for shipping in China. i.e you will have 100% of the invoice value about 28 days before the goods arrive in the UK.
In my experience, there are real risks that sometimes you will not receive exactly what you paid for or (b) goods arrived incomplete or damaged. Either way, you will have a problem to get your money back or replacement products sent foc. Your relationship with the manufacturer/exporter will make all the difference. I have personally heard of many instances when these type of purchases go wrong and even experienced business people who have been conned & have lost money.
The best way to do this tyoe of trade is to have someone in China you can trust 100% - they can take care of all of this i.e visit the manufacturer, make sure your goods leave the exporter in good condition (i.e complete, accurate, well packed etc etc). They can oversee the loading of the container. They can also find you a good freight forwarder locally in China so you get good rates.
Of course, many people also make successful trades without any hitch - I've just painted possible issues that you SHOULD worry about to make sure you don't lose money.
I own a company based in the UK and with offices in China and Hong Kong. We import a range of products from China into the UK. If you are interested to know more, perhaps we can help you - pm me.