MedEntry is very overpriced and they have apparently been using questions from the ISC UCAT book. I recommend purchasing Medify. It's far more affordable, it has over 10,000 practice questions, mini mocks, mock exams and video tutorials for each section. They've also been catering to the UCAT (UKCAT) for ages due to being a UK company. If you've fully used up Medify, THEN you can purchase MedEntry for more practice questions/mock exams.
Also, I highly recommend you watch some free youtube videos on the UCAT and do all the official, free practice questions and mock exams on their website before buying any questions. They give you the best possible insight into what the questions are like, as they were written by the company that writes the UCAT and are imo the best practice tool you can use.
If it were me, I'd go in this order: official questions/exams --> Medify --> If you have more time, MedEntry.
Kaplan is also useful if you want to improve in Verbal Reasoning, as their VR passages are very long and questions on average are more difficult than the real thing (for VR).
EDIT; May be worth it to save some official UCAT mocks for closer to the exam. This is up to you however, whatever works best.