If you require a medical certificate from your doctor for six working days' absence or less, a private certificate will be issued for which there is a charge.
After the first week certificates are obtained as part of a consultation with a doctor, this may be available with a phone call rather than a face to face appointment. If you are under the care of a hospital doctor they are obliged to provide you with a medical certificate and not the GP, they should provide you with a certificate for your entire period of sickness after an operation etc.