I will amend my comment. If your kid has enough get up and go to finish the term in the UK on June 17th and be moved in to a sublet and ready to start work on Monday the 20th (your dates may vary) then there is no issue.
For other kids- it is something to consider. Not a deal-breaker, but something to consider.
My kids did internships, paid jobs, fellowships, etc. during the summers. Some of them had flexibility (choice of start and end dates), some had no flexibility (orientation is assigned- so you don’t choose either the city or the start date) and some had flexibility on a case by case basis (finishing up an on-campus research job generally got you an exception; wanting to spend a week at the beach with your buddies after your last final generally did not). It varies.
Being overseas is just one more thing to consider.