While I haven't used the UK version of Amazon I thought they were somewhat trustworthy. IDK. If you want inexpensive and trustworthy, there is always Fasttech, but you will need to be willing to wait. It can be a great option however, they are truthful when it comes to "authentic" and "styled" (clone) and although they are slow, they are reliable and honor their warranty period. I'm not UK based so can't really recommend a vendor but you could look near you and see if there are any well-reviewed brick and mortar stores.
Anna