If you do not belong to a union and have a disciplinary then you are on your own.
As far as accidents at work are concerned, there are a multitude of companies advertising to fight such cases on a no win no fee basis.
Check your home insurance, you may find you can get free legal representation from them.
Obviously it is better to be in a union as none of us know what might happen but it is difficult if you do not have much faith in the union.