Long Haired mum needing your advice on hair test..more than a job to lose

hi everyone,i came across your site looking for information on hair testing.
To cut a long soty short i am in the middle of a custody battle with violent ex husband his mother has them at the moment and they refuse to give them back.Its going through courts and this week he decided to demand i have a hair drug test going back 6 months.
Both me and my current husband are HEAVY daily cannabis smokers.I have smoked it for about a year and a half.My ex has no knowledge of my smoking it he is just clutching at straws but never the less i have to have a hair test,if i fail i WILL lose my children.
I have read so much info on here and other sites regarding the different methods to use and am quite alarmed by some of the painful methods people have used although i fully understand why they do it.
I have very long dark brown hair which is approx 8/10 " below my shoulders.i really dont want to go with the bleaching method but am interested in the Macujo Method.
Does this method hurt? or damage your hair/scalp?
and do you think it would work as i smoke quite a lot.
Im also based in the UK so i cannot get some of the ingredients listed on the method so could you advise me on alternative products to use.
The apple cider vineger isnt a problem i can get that but i cannnot get Tide or neautragena T/SAL ,we have neutrogena T/Gel and im not sure if that contains the needed ingredients.
Can someone advise me on all this please as i am desperate,my smoking pot doesnt affect my parenting ,i dont smoke it near my children,they have never seen me smoking it,and the last thing i want is for him to win custody so any advise would be sooo much appreciated thankyou in advance

and also is there anyone on here that has had a hair test in the uk.and could tell me what they do? i know the hair test procedure but wondered if they call you and tell you when you need to go,write to you etc? is it done at their testing place or at doctors?