Generally, UK schools give exams before the summer holidays and ask their students submit paper in September. So MSc candidates can not have any transcript to send US schools in December the year before. The US phD program appliction finishes in December or January.
given the limited time (one year master program), the above mentioned event comes with trivial probability. you need time to master the knowledge, set up relationship, and WRITE out the paper. do you think you can manage to do all things within 3 or 4 months time? (you have to send your applicaiton package by the end of jan, safely speaking.)