UK law protects heterosexual non-biological fathers conceiving with donated sperm.
A man who is married to the birth mother at the time of conception is automatically the legal father of his child. The rules apply to conceptions which take place with his consent through IVF or artificial insemination (not sexual intercourse), whether at home or at a clinic in the UK or overseas. A married father is named on his child's UK birth certificate and automatically has parental responsibility, giving him the authority to make and be involved in decisions about his child's care.
The law applies unless it can be 'shown' that the husband does not consent, something which must be proved as a matter of fact. In some cases (for example where separated wives are conceiving as solo mothers before their divorce is concluded) it is sensible to collect evidence which can be used to 'show' there is no consent.
An unmarried non-biological father is the legal father if conception takes place at a licensed clinic in the UK. For children conceived after 6 April 2009, both partners must complete and sign HFEA Forms WP and PP before conception (and should first have had counselling and been given proper information about the forms). There have been a number of recent cases in which fertility clinics have not managed this process properly, and as a result the legal fatherhood of unmarried fathers through sperm donation has been jeopardised (in each of these cases the High Court ultimately made a declaration of parentage to resolve the difficulties). For children conceived between 1 August 1991 and 6 April 2009, the father must have been having 'treatment together' with his partner at the clinic in the UK.
Like any other unmarried father, he will be financially responsible for the child. However, he will only have parental responsibility (the right to make and be involved in decisions about his child's care) if he is registered on the birth certificate (which requires the consent of both legal parents) or if he takes steps after the birth to acquire parental responsibility as a legal parent.
If an unmarried father is not the legal father (for example, if the HFEA forms have not been completed in time, or conception takes place overseas) he can take steps after the birth to apply for step-parent adoption.