Based on my experience I would recommend having and professional passport photo done to avoid application moving over to a manual system.
Very good advice for peace of mind – my local Kodak photoshop did mine, a person takes the photo and I walked away with 4 prints and a code for the online application for £10.95, only a couple of quid more than the self service booths – and a guarantee that if it’s reject they will do it again for free.