So I am unwell today (covid vaccine and trust me to get the side effects)
so I spend some time going through all the suggested brands putting them into Good on you website if you are interested they explain here how they base their ratings to see if it is sustainably sourced. Their ratings are
We Avoid / Not good enough / Its a start / Good / Great
This is what I came up with
We Avoid
All Saints
Jaeger
Joules
Reiss
Not Good enough
Boden
Celtic & Co
Fatface
Hobbs
Hush
Jigsaw
John Lewis
LK Bennett
Mint Velvet
Olive Clothing
Phase Eight
Sweaty Betty
Toast
White Stuff
The White company
Whistles
Sezane ( though Curiously conscious rates this higher I would argue at last an It’s a start if not good)
It’s a start
Arket
Banana Republic
Cos
& other Stories
Tommy Hilfiger
Good
Baukjen
Marks & Spencer (this one surprised me)
Great
Aspiga
Scamp & Dude
Thought
Peopletree @Notlostjustexploring I may have placed an order 
Not on “good on you” so web searched
Unable to find
Patra silk - (too many suggestions for me to know what one it is)
Kin- Can't find on its on but John Lewis is a Not good enough
Caroline Charles – their own website says sustainable but I can't find outsider comments
Good
Me & Em -
Palone -
Sahara London
Modern Rarity
Great
Blackhorse Lane Ateliers
Mudra Collection-
Huit -
Poetry –
Christopher Raeburn
Katherine Hamnett
This Website suggested 25 sustainable clothing companies and some of them look interesting