Have you tried All Metal Services in Birmingham, I have been having Ali off them for many years and they have always been able to fix me up , they seem to have it in ‘O’ state as well as T3.

I assume you are wanting it in ‘O’ as it forms easier, dont forget it needs heat treatment to put it up to T3 for aircraft use. I have found it always warps doing this and takes a lot of work getting it straight. Far better if you have access to a heat treatment kiln is to use it in T3 whch is then softened to ‘O’ for you to form which then goes back to T3 over a few hours or after working it. Sometimes it has to go back in the kiln for a second go if it starts to harden up before you have finished shaping.

Hope this is of interest

Ken