How's it legal for NHS trusts to have different formularies?
Assume you live in Cambridge, but your migraine can be only treated with a triptan on Oxford's formulary, but not Cambridgeshire's, like Eletriptan. What do you do? Must you go to a NHS hospital in Oxford?
There is no legislative requirement for individual hospitals, primary care facilities or secondary care facilities to provide the same treatments or specific level of care across NHS England, but there are legislative requirements to reduce the inequalities in healthcare across the NHS.
The Health and Social Care Act 2012 introduced general legislation requiring the NHS to reduce the effects of healthcare inequality, but it does not go into specifics such as requiring all hospitals to fund the same treatments.
As a result, patients have a legal right to choose where to receive treatment in secondary care facilities (ie, hospitals) once they have a referral, but no specific right to choose any GP they wish (GP surgeries have specific catchment areas, outside of which they can refuse you as a patient - hospitals in England have no such limitations and can only refuse you if they do not provide the treatment you are seeking).
Part of the point of splitting up NHS England into various Clinical Commissioning Groups (the descendant of Primary Care Trusts, which ceased to exist in 2013) is that healthcare requirements are not the same across the country, and some areas need more funding in certain healthcare areas than others. Requiring the same level of care for all healthcare issues across the board all over the country would mean some areas are underfunded for some outcomes and overfunded for others.
In short, you need a referral to a specialist from your GP, and then you can choose to go to a hospital in a CCG which funds the treatment you are seeking. This may not always work, as the treating CCG can request the referring CCG to fund the work and thus you may be rejected anyway. You also have the option of funding the drugs yourself.