Well, if you are going to be low-cost, LHR slots are not the cheapest in the world are they... time for SB to do one of two things -
1) force the EI board to demerge its slots in a way that allows the Irish government to take ownership of them and then offer them to any EU company including BA & BD (would have to under EU rules I'd say) who would operate full service and cargo.
2) tell Willie enough is enough - one Ryanair is sufficient.