I believe many concerned in my care made mistakes, do I have to sue them all?
If the care you received was provided by an NHS hospital, the Trust which governs that hospital will be responsible in law for all the people who work there, so there will only be one Defendant.
If your care was provided privately the position is more complicated and you may have to sue more than one party, for example the private doctor who treated you and the hospital at which the treatment was provided.