Hi gde. Welcome to the forum.  Please be aware that I'm not a medical professional.

Provided you are an adult with appropriate mental capacity, then you may refuse any NHS treatment. This is explained in this web page: Do I have the right to refuse treatment?

The GMC also requires doctors to honour a patient's refusal to have treatment (again, provided that patient has mental capacity): Personal beliefs and medical practice

Note that the refusal should be informed; in other words, you have had the implications of such a refusal explained to you.