'Market Driven Pricing' involves evaluating what your competitors are charging at any given time so you remain competitive. Now bmi, in their mind, don't have to do that because, in their mind, they don't have any competitors on the LHR route.

Therefore, my advice to the OP about a "legitimate way to flag it to bmi" is simple; fly Aer Lingus who have fares from £23.99 (£10.00 more if you have a bag) most days during the same time period.