Eastern Europe, underserved by LHR. If there was a potential feeder route network that could work, including some eastern Europe destinations would work.
I would never suggest BMI try in core locations like MAD, CDG, BRU etc.... Virgin whether it be Group or Atlantic can make BMI work, lots will be stripped for long haul either way, but it's going to stand a better chance (for jobs moreso) in Virgin hands.
SRB is used to running Virgin branded co's at a loss for 3-5 years to make them work in the long run.