Just and idea!!
BACF this summer will operate the usual Saturday MAD/LCY service and the Sunday LCY/MAD as they have done since starting the route. Surely wouldn't this route be more popular with leisure and some business pax if BACF at least offered a Sunday flight ex MAD to cater for those pax on weekend breaks. Especially during the summer season. I know it would do well.
What they could do is operate a Saturday MAD/LCY/MAD service departing at the same times as the Monday-Thursday BA8752/BA8753. With the aircraft day stopping in MAD before operating a BA8754/BA8755 on a Sunday. It is better than the a/c sitting around in EDI for close to 30 hours.
Also I noticed BACF will operate 3 flights ex LCY to EDI on a Saturday departing at 08:40, 08:45 and 09:30. ( 2 x E170, 1 x E190SR). I think they will struggle to fill those seats.