For those who know the EU cancellation regulations better than I do, am I entitled to anything that is going to partially offset an on-the-day expensive BMI ticket from LHR to BHD instead ? Rearrangement/cancellation with one working day's notice.
The EU regulations are about EU wide minimum standards, they are not comprehensive in any sense. The issue primarily is one of contract law and here breach of contract. The EU regulations do not cap anything you are entitled to under your home country's laws.