Those "horizontal bars" are reflected light. Fresh medal ribbon is usually quite glossy, and can give reflections like that. The ribbon is for the Defence Medal.
The Defence Medal was more of a campaign medal than a bravery decoration, and several million were awarded. For UK residents, the qualification was 1,080 days of service in the UK, or 360 days overseas service in areas not subject to air attack or invasion, or 180 days overseas in threatened areas.
Incidentally, the picture is necessarily from 1945. The Defence Medal was not instituted until May 1945, and general issue probably took several months, while the subject was demobilised in late 1945.