I am an EEA National, trained overseas
You will need to obtain registration with the General Medical Council (GMC) which is the body which deals with the registration of doctors within the UK: www.gmc-uk.org/doctors/before_you_apply/imgs.asp. The link on the GMC website is for International Medical Graduates.
Unfortunately, the London Deanery is unable to arrange clinical attachments. Doctors use various methods to organise a clinical attachment. It can be useful if you already have a contact working in a UK hospital, who is willing to supervise you on attachment or can refer you to a colleague. Other methods are to approach the Human Resources Department, the hospital Postgraduate Centre Manager or the Head of the Department of the particular specialty you have an interest in. It is worth keeping in mind that it may be easier to get a clinical attachment outside of London. There are more overseas doctors in London competing for clinical attachments. Below is a web-link to a site that has contact details of all the NHS Trusts in the UK: www.nhs.uk/ServiceDirectories/Pages/AcuteTrustListing.aspx
You may also wish to refer to: www.bma.org.uk/international/comingtouk/clinicalattachmentguidelines.jsp.
For convenience, you may prefer to look at the hospitals near where you are living if you are already in the UK.
Postgraduate medical training in the UK is provided in hospital training posts in the NHS. These salaried posts are filled by open competition and are advertised in medical journals e.g. BMJ and The Lancet. While in a training post doctors will receive in-service training, academic instruction and may attend additional courses.
If you require information about a particular specialty, you should contact the relevant College or Specialty Association directly. The College websites are listed here: www.bma.org.uk/international/refugee_doctors/refugeedoctorslinks.jsp.