Go to the main page. you get a map where you can choose your departure airport, the destinations served then light up. HAJ lights up when you click on EDI.

I’ve since learned it is a codeshare with BA, as Doors4 suggested.
Strange though, as BA will not allow me to book EDI-HAJ either.
What’s the point of a codeshare if you can’t book on the one single system but need to book individual flights on individual systems?!

Well, They’ve had their chance.

FR EDI-BRE it is then!