I have no idea how they grade tutorials. Sheffield has Programme Specifications on their website, maybe Birmingham has something similar as well. Anyhow, it says that there are data analysis sessions (same as tutorials?) which consist of instruction, discussion, and practice; and then there are tutorials mentioned separately, but both type of classes are assessed and supervisors will provide oral and written feedback (which counts toward the practical module grade).
A doctor can help you in terms of diagnosing you. Mine is good, scientifically-oriented and not too touchy-feely. She works with both kids and adults and the center provides numerous therapies for kids with autism spectrum disorders so I knew she'd be familiar with the condition (many unfortunately aren't). If you choose to go to a doctor then pick a young one - Asperger's only came to exist as a formal diagnosis in 1994 (in the DSM) so going to someone who has completed their residency in the late 1980s or earlier is probably a waste of time.
I decided to change course because the original one wasn't what it was made out to be. All the brochures say that you can take up to a third of your modules from the other two biology departments (Sheffield has three) and I counted on it, I made my choice to go there because of that, but when I got there it turned out that it's not possible (all the classes are completely full, etc.). I intend to go all the way to a PhD so I thought it'd be best not to specialize too heavily too early on and decided to do a broad biology degree. But then I was forced to rethink my plans and since I'm certain that my future lies in the molecular biosciences I might as well go into it right away. Almost all straight biology degrees are focused on organismal biology anyway, and that's just boring. Sheffield's biochem program is broad enough, specific enough, without the ubiquitous biomedicine slant, and in the top 5 for biosciences, and all that is exactly what I want. I just wish I had realized that a little bit sooner. Oh well, there are dozens of reason why it's better this way anyway. By the way, I just received my very own Molecular Cell Biology by Lodish (basically this subject's bible) and now I spend all my days reading and memorizing that (yeah, special interest transformed into an obsession) so that when I get there in 9 months I can show them that no "disability" is going to hold me back.
Heh, I might not be as "your age" as you might think. It took me two extra years to get through high school because I had some serious problems before being diagnosed, and now I'm missing another year. If everything had gone according to "the schedule" then I'd be graduating from a BSc program this spring. However, I'm not, I'll be starting my MSci just a few months after turning 22. Mentally and experientially, however, I'm not over 13 or 14.