You shouldn't need your GP. I'm a student midwife and have supported a few elective c/s due to emotional trauma during my prac placements.
If you've had a traumatic birth which has left you with a fear (very valid reason) of vaginal birth then you shouldn't find it too difficult to obtain a c/s.
Ask to see an OB and talk it over with them, be open and honest about your previous birth and how it's affected you. Stay strong and don't waiver. They WILL try to sway you because that's their job and they have to do that, but if you can explain your reasoning they are unlikely to deny you.