DCF is completely at the discretion of the London consulate. You must request DCF submission prior to filing an I-130 through USCIS. For a DCF case, EVERYTHING is done at the consulate level. In fact, a consulate is not authorized to accept a case which has already been filed with USCIS.
Contact the consulate and give them your exceptional situation evidence. They should provide you with guidance.
If the consulate denied DCF (although a job offer is normally accepted), you would have to file through USCIS and request an expedite at USCIS, NVC, and the consulate. Good luck on your journey.