Yes, the above comments are all spot on!
As pointed out, a UK contract means nothing in China when push comes to shove. They will only pay lip service to any document like this at best. Better is to have a good company to work with, and have a good relationship with them.
My business is product development, supply chain management and production in Asia.
As such, I am careful about the companies that I do business with and vet them first before working together.
Having a spec and confirmed BOM (Bill of materials) in place, plus a full technical file that the factory understands is key. If there are any testing procedures that need to be followed then you must satisfy yourself that these are being followed.
Do you have a technical file for the product? Who designed and developed it? Yourself? Or the factory there? Or do you just have a sample?
Of course in manufacturing, there will always be products that fail for reasons that you didn't expect. You need to monitor these and adjust the QA if needed.
Again, are these products certified and tested to standards for sale in Europe? CE marking, RoHS compliance and the like? Do you have copies of the test reports for any approvals etc? Are the test done by a reputable test house over there? Etc etc.
As a retailer of these products, you will need to agree with the factory how defects will be handled. Since you will not be able to send them back - in most cases China customs won't allow the goods to be returned.
Payment terms need to be discussed and agreed. It you want something out of their norm, don't be surprised if the cost goes up to finance it...
Have you been to see the factory/supplier? Do you know what they have in place? Would you be able to determine if their systems are robust?
If you want to discuss more, PM me and we can take a call. Might be easier than typing war and peace here! I am happy to give advice and help if I can.
Welcome to doing business in Asia!