So it turns out the field might be a little more cursed than I thought. I've dug stuff from in the woods around the field and the roots tend to be more shallow and radial. The field has such light loose soil, and the meadow grass on top sucking up the moisture even on an area probe to flooding, combined with Oaks natural tendency to throw down one crazy tap root... The roots are baaaadddd on these!
I dug 4 as they were so damn easy to lift, literally 5-10 minutes each. All of them basically one tap root with next to no fibrous roots. I've shortened one of them but the other 3 just took the lot.
Put them in a deep trug for now complete root ball not washed off. Priority is going to be getting them to survive, almost all the work for next few years will be regrowing better roots and developing radial growth. In the early spring I will definitely be using the sweating technique which is why all 4 went in the same container so I can bag the whole thing.
If they get some good growth and recovery next year I may try to ground layer one and see how well that works with Oak as I can't find much comment on them.
I'm thinking 3 of them might end up planted together eventually.
Excuse the lighting I didn't get time to sort them up until after the kids were in bed! Next job is to rig up some lighting in the greenhouse.