A gap year is a good idea if you’re looking to strengthen your application – for example, gaining more work experience as you said, working on your UKCAT score, personal statement (as long as you can demonstrate that you’ve worked on your application during that year!)
Regarding the gap year and attending uni afterwards, this depends on how you personally study and can adjust to learning after periods without studying – we’d suggest perhaps speaking to other students who have taken a gap year and asking them how they managed their workload after a year out. Another useful thing to think about might be how you find starting a new year of school in September after the summer and how difficult you found it to adjust.
Hope this helps! 🙂