These situations are so often so distressing and upsetting to patients and I am sorry you are caught up in a medication change.
However, I really don't think that you understand what drives these changes. Please speak to your GP - don't go in with all guns blazing, but seek to understand what has happened.
Trust me when I say overworked and underresourced GP surgeries need the work load, the upset and the inevitable fall-out when people are upset and angry as you are and always blame GPs/individual surgeries for processes that are Healthboard or government driven.
And as to 'specialists know best'? Don't make me laugh.
The active ingredient is identical between branded and generic meds, the inactive ones often aren't. Some drugs must be prescribed by brand because of differing bioavailability, the vast majority don't.
You need more information first of all.
You also need to think about whether you think it is worthwhile changing medication to equally effective but cheaper ones is worthwhile if it keeps another, I dunno, oncology nurse in a job rather than reducing services so you are allowed to not even try an alternative drug.
The pot of money is dwindling and all of us have tough choices to make.
I keep hearing 'I know the NHS is on its knees, but..." followed by one that particular individual should be an exception 