Considering 52 pax makes a 68% load factor on the E170, and having been one of those 52 I know there were in fact 63 booked, an even better 83% load factor, the route is doing remarkably well and with £75+ fares, I wouldn't be too worried about the future of this route.
Eastern's new buy on board will most likely be making a valuable contribution as well, from what I saw everyone bought something and between 2 of us we spent £42 on the flight in booze and food. If that's representative of the average holidaymaker I think Eastern have made a good little move with these routes. Even the inaugural GIB-BHX had 20 onboard and the inaugural BHX-GIB was full. If I was Eastern I'd be very quickly thinking about what other GIB routes could be capitalised on while it's one of the few green list places available. I'd be looking towards BHD, NCL and LBA.