One First Matter All
Mame
Sure you can collect in Autumn, but unless you know how to care for what you've collected, your wasting your time and killing trees for no real reason. There will be folks who will tell you that process will teach you how to collect. I don't think that's true. Collecting in spring teaches you more, since the tree is actually growing after you collect it, has more resources and is more responsive.
I appreciate you taking the time to post, but some of what you said seems to be undercut by your final statement. Collecting is not an either/or scenario. I can collect in the fall and the spring. Each might teach me different things. From what you say, it sounds as though I might be in for some disappointment with regard to the tree I collected this year. I'm ok with that. Luckily, that disappointment will turn into more hope as spring arrives, and I get another chance to collect. So, while I appreciate your advice (and the link to some helpful Midwest-specific bonsai info!), I guess I don't get the huff. Everyone knows that getting really good at bonsai involves trial and error. Internet advice helps (assuming it's actual advice, not just finger-wagging), but it cannot replace hands-on experience.
Also, the article I posted suggests that collecting now does not mean waiting for the roots to grow: "The roots of deciduous trees are very active in the late Summer and throughout the Autumn." Unless UK roots are different than American roots, I'm going to trust that the roots are going to do their best to get in shape for winter. They (and I) might not succeed. The fact that roots continue grow into the autumn dilutes your other points (need for better storage, for instance), which start from the premise that roots do not grow at that time.