You can work as Cabin Crew at 18 in the UK as that's you legal to serve alcohol, and obviously you have to be 18 for the safety/security aspects. You may be able to do the job and study - I only work around 10 days per month doing it and have plenty spare time. You wouldn't be allowed to do it for work experience simply because you'd have to go through the full intensive training course for any airline to allow you to be in the air, but I believe it might be possible for you to actually do the job whilst gaining your qualifications. Good luck!
Source(s):
I am Cabin Crew