When my three kids were young, they all refused to wash their hair. But they always insisted on bathing together. So I decided to put them in charge (sort of) and gave each one bottle of warm water. When they were all assembled, I had each one hold a bottle above their (own) head, and, pour on cue. Later we put baby shampoo their heads first and they liked that, too. This might work for you.
One thing I learned through reading and taking all kind of parenting classes, was get that the one who refuses to do the activity should be placed in charge of "leading" or making sure everyone else complies. This worked when one of them refused to buckle his seat belt. He was then in charge of "seat belt check". He even insisted that we respond "check" if we had our seatbelts fastened.

My boy hating his hair being washed to but i told him to close his eyes and look to the stars then we count 10 rubber ducks as i slowly wash him and it helps him.

Thanks I have tried both of those things I don't know if its a battle of wills or if it is something more. But thank you for taking the time to help its very much appreciated

I use a wash cloth to wash my grandson's hair.

We have a hair appt booked so hopefully shorter hair might make it so much easier thanks everyone for your help. I'll post in a couple of days and let you know how we get on. Fingers crossed. Xx