Ooh, I found a nice looking Maple and I got it home and repotted it. No pruning done, I just opened out the roots so they fit in a smaller more shallow pot. Well, I did have to remove some roots, but it was minimal and I took care to not touch the white ones.
It had some drying on the top leaves which were cut out and the soil changed to give better circulation of air and water.
Here's a pic, I don't think I can do too much in terms of form, but any trimming will have to wait till December/ January anyway. I'll leave it alone now until winter ->