Choice on what, specifically?
Choice of hospital is up to you now - early this year the government made it possible for all patients to have a choice of hospital. You just need to ask your GP to refer you there.
If it's choice of prosthesis - that is not something that is within the patient's choice and nor should it be. Choice of implants is a skilled thing that should be done by the surgeons - that's their job. They spend a considerable part of their lives developing skills at using a particular prosthesis and it's no more appropriate for you to expect to dictate to them which product they use than it would be for you to dictate to your dentist which equipment he uses to treat your teeth.
Besides which, once the implant is in, there is no possible way you would have any idea whether you had products a, b or c put in. Despite the manufacturers claims on their literature and websites, it's a fact that they are all pretty much of a muchness in the end.
If you are happy with the surgeon you have chosen or been referred to, then trust him regarding which implant he uses. He'll have been using it for many years and it will therefore have a good track record in his hands. Not that any surgeon would change, but if one should be coerced into using a prosthesis he'd not used before, the complications risk would become astronomical.