ksand has done an excellent job here so far! But if it helps, I'll chime in too.
I studied at the Uni of Nottingham from 2010-2011.
The visa process did not take too long, and it would be helpful if you clarified what exactly you've booked for July as that is a little confusing, but ksand listed all the most relevant links, so maybe that will help some?
One thing that occurs at some point between the university issuing a CAS and actually applying for the visa is actually having your loans certified. The loan certification process also requires a CAS. (Unless of course things have changed since 2010, which is definitely possible!)
In addition, depending on your Neuroscience course, you may have to apply for ATAS approval (Academic Technology Approval Scheme) as part of the visa process. I had to for my Biochemistry Master's, but this may be due to the nature of my course- which was ~95% research. If ATAS approval is required it will be noted on your CAS.
I'm very excited but I'm feeling a bit lost due to the limited information there is available regarding US students studying in the UK.
Check out other posts on this forum, and I'll try to dig up a link to a website that at one point I thought was useful.. There's a lot more information than you may currently think. A lot of people also have personal blogs which can describe certain aspects about UK life. There's also a thread somewhere here on UKY about things we tend to miss most about the US, to prepare yourself, or, in the event that you decide to stock up on certain items before coming-- for me it was Secret deodorant (now I just use Mitchum), and Neosporin (I must be allergic to Savlon cream or something!? It irritates my skin)
What did you pack for a year long course?
I checked 1 large(ish) suitcase, 1 carry-on suitcase, and 1 backpack as my personal item. I personally figured it wasn't worth it to pay extra to haul over all my stuff, when I could pay the same to just buy new stuff. There's also the fact that there's typically less space in apartments/flats/closets, etc here, so you may not have room for everything you bring over! Pretty sure I left packing to the last minute...
What funding resources are available?
As ksand mentioned, there will be little funding available to you as an international student once you arrive, as you will have already demonstrated that you can support yourself for the year without additional funding. However, you will be allowed to work Part Time (20 hours/week) during your studies, and Full Time during school breaks. Personally, I did not have enough time to have a job on the side as I was in the lab until around 7pm each night, and wasn't about to be a bartender/waitress after having spent all day on my feet. But obviously experiences/expectations will vary, and I'm sure it'll work out just fine!