what day are the final percentiles ucat releasedWatch
They should be released when all applicants have taken the exam. The final day is on the 29th September (proctored UCAT), so I would assume either that evening or the following day.
They need to analyse all the candidates scores to calculate the final deciles and percentiles. There are also some contingency dates after the 29th September for the rare few people who may need to do a retest.
UCAT will usually inform candidates when they plan to release the final results like they did for the interim.