I think the only One-Elevens built with Seatback catering were for Court Line. When they went under these aircraft went different ways, a number went to Dan-Air, who continued the concept. Did anyone else ?
First ever jet flight was a British Eagle One-Eleven, Liverpool to London, off the old short runway. G-ATPI "Supreme". Visiting aunt was returning home to Canada, it was school hols, she says to aviation-interested teenage nephew "would you like to come with me on the initial hop to London, coming home on the train ?". No need to ask twice. Pretty thin load; Eagle went under a couple of months later.
And last One-Eleven, 1993, BA Birmingham to Edinburgh, in their final weeks. I knew it was, and had sort of arranged an oddball sector to get it. Notable was the condition of the cabin inside. It was immaculate ! No trace of anything faded, worn or uncleaned. Seat fabric completely unfrayed. Well done Birmingham maintenance.