I've been abroad for a few weeks and was out of touch with local events at home. Have TUI confirmed that the 757s won't be at BRS next summer and will be replaced by 738s? If that is the case, as Marko points out, it will mean a significant drop in seat provision.
With Thomas Cook looking vulnerable - at least in the sense that their painful summer 2018 experience to the summer sun generally (not just from BRS) might lead to a reduction in their offering next summer - BRS's reliance, and stated preference, on existing airline partners might have to be re-evaluated.