From the Medical Defence Union site:
Children under 16 can truly consent to treatment only if they understand its nature, purpose and hazards. That ability will vary with age, the child and the nature of the treatment. A ten-year-old will, for example, usually understand what is involved and may be able to give reasonable and informed consent when asking a doctor to dress a cut knee. The same child is, however, unlikely to be able to consent to major surgery. To be able to consent, the child should understand not only the nature of the proposed treatment, but also fully understand and appreciate the consequences of the treatment, and equally of the failure to treat.
and, regarding termination of pregnancy:
The MDU has been advised that when a girl is under 16, her parents should be consulted unless the girl forbids you to do so. You should obtain the patient's consent and the written authority of the parents. But their refusal should not prevent a lawful termination to which the patient herself consents, if you are satisfied that the patient is mature enough to understand the nature of the operation, common complications and the issues involved - the same approach as in the Gillick case. When you are satisfied with the girls capacity to understand, you may proceed in her best interests, though every effort should be made to involve her parents.
Regarding confidentiality:
Children over 16 should enjoy the same rights to confidentiality as adults under the Family Law Reform Act 1969, which enables children of 16 and over to consent to medical treatment. You may have to use your discretion with children under 16. When the child is mature enough to understand what is involved in the proposed treatment (i.e. is 'Gillick competent'), you should respect the child's wishes if he does not want his parents to know about the proposed treatment. However, you should make every reasonable effort to persuade the child to involve his parents or guardians or to tell them himself. If you decide to disclose information to a parent or legal guardian against the child's wishes, then you should tell the child that you are about to do this, except in very rare cases. The overriding consideration must always be what is in the best interests of the child. If a child is not 'Gillick competent', whoever has parental responsibility under the Children Act 1989 must give the authority to disclose. Again, in deciding whether to disclose information, your overriding consideration must always be what is in the child's best interests.
IMO, the law is fine as it stands.