First of all, congratulations on getting into UPCSE and good luck on your future studies!
It might be a bit late for me to say this but it depends on what sort of qualifications the college in California could give you. If they are not equivalent to A level, I think UPCSE would definitely give you a higher chance of progressing to UCL undergraduate studies. Plus, you have a guaranteed offer for many biosciences courses at UCL when you apply on the UPC.
The entry assessments take place during the first week, though if you completed the first entry exams honestly, this should not worry you at all.
Biology and chemistry modules are the most intense elective modules on the UPCSE. Maths and physics students have less hours. Prepare yourself for 6 hours of lab, 4 hours of lectures, 4 hours of tutorials and having to produce 2 lab reports and 2 courseworks (on top of other EAP and S&S assignments) every week. For biology, there is a field trip around May to Nettlecombe Court Field Studies Centre, where you will work extremely hard for 5 whole days.
It is definitely not “easy” to progress to a UCL undergraduate course. Although it depends on the course, you will need to achieve extremely good grades of mostly As during UPC in order to progress. What undergraduate course(s) are you thinking of applying? Never enroll yourself into the UPC thinking it will be an easy ticket into UCL undergraduates. It is not. You need to work very hard. From my understanding, although many people get offers, not all of them meet their offer and actually progress. Most of my friends last year were unsuccessful.
I have finished the course. Honestly the course was overall a more positive experience for me rather than a negative one, because I’ve really learned a lot, even though it was highly difficult at times and put me through a lot of stress. It is very challenging and is definitely not for everyone. I know lots of people who seriously struggled, even developed mental health issues throughout the course. I am happy to have done it and now I am in my dream course at UCL.
For bio/chem tutorials, students are divided into smaller groups of around 6 or 7 and they take place twice per week for each module. When a student seriously falls behind the course coordinators will provide extra one-on-one or group tutoring sessions (though I don’t know how effective they are really since I haven’t attended one). Everyone on the UPC is also assigned a personal tutor at the beginning of the year though they do not really teach; they mostly provide guidance and check on your progress once a week. They make sure you meet all your deadlines, attend all your classes and your grades are maintained. The UPC does not put you in study groups; however, it shouldn’t be difficult for you to gather some friends and study together.
I hope I’ve answered all of your questions. Feel free to ask more