I don't massively understand how unions work. I am a member of UNISON, because it was cheaper than the RCN when I qualified as a nurse.
When I first joined, it was £14 per month. It is now £20.30 per month, but works out as £16.24 per month after tax relief.
Nurses and midwives also pay £120 a year to the Nursing and Midwifery Council, which is the regulatory body, not a union.
I mainly joined UNISON to have access to legal help if I ever needed it (which I haven't, thank God).
There are a few different unions people in healthcare can join, I think anyone in any job can join unions like UNISON, Unite and GMB Union. Then there are profession specific unions, like Royal College of Nursing (RCN), Royal College of Midwives (RCM), British Dietican Association, Chartered Society of Physiotherapy.
It is confusing as there are so many unions, and I think it's hard to coordinate negotiations with so many.