Section 5 - referees and identity
You must include a recent passport photograph of yourself, clipped or stapled to the space provided. The photograph must show the whole of your face, it should not be covered by your hair (except a beard, sideburns or a moustache), a scarf or traditional dress. You should not be wearing dark glasses, a hat, a hood, a cap or a scarf.
Your application must include details of two referees. The referees should have known you personally for at least three years. One referee should be a person of any nationality who is of professional standing such as a minister of religion, civil servant or a member of a professional association such as an accountant or a solicitor. See the list of Acceptable professional persons. The other referee must be a holder of a British citizen passport and either a professional person or aged 25 years or over.
Both referees must be:
not related to you; and
not related to the other referee; and
not your solicitor or agent representing you with this application; and
not employed by the Home Office.
Per the red text above, if the A&E doctor has known you personally for 3 years then they should be fine.