If you need GP advice out of normal surgery hours, you can still phone your GP surgery but you will normally be directed to an out-of-hours service.
When you call the out-of-hours service you will be asked about your symptoms and a message will be passed to the GP on duty, who will then call you back to advise you on what to do.
During out-of-hours periods you can also call NHS 111 who will book you an appointment.