An extremely broad category of course and one which embraces a number of possible careers with a creative element. What they have in common however is the significant challenge of making a living in a business which is always hungry for talent and yet notoriously difficult in which make a successful career. The entertainment industry - broadly defined - has a career pyramid which is very narrow at the top. Those who have successfully scaled its heights are by definition extremely visible but, like lottery winners, they stand on the shoulders of their far more numerous competitors. Success is generally a question not just of talent but single minded perseverance, networking skills and/or luck. Recommended only for the dogged and the driven. Some of the obvious heads:

ART
Unless you are already very well connected with potential buyers interested in your work, going back to school would be a good idea to build up your profile. Focus on the kind of art you would like to make then take a look here for courses or even art holidays to unlock your potential: http://www.britisharts.co.uk/artcolleges.html.
If you already have work, get it online here asap:
http://www.saatchi-gallery.co.uk/yourgallery/.
Or if you just want to work in an arty environemt, try http://www.artsjobs.org.uk/.

PUBLISHED WRITING
As the number of book titles grows, and the cost of printing declines, being published has arguably never been easier. Many small publishers will take a chance on a first time novelist or writer. But conversely, a crowded marketplace makes it harder to make a living. Most writers earn a modest sum. Advances (if available) are more commonly four figures than five. And, once published, many authors end up being their own personal PR agents, pounding the pavement to drum up sales and elusive media attention. If you already have a first draft, join this website - set up by Harper Collins - and chance your first chapter with other wannabe novelists who will offer constructive feedback:
http://www.authonomy.com/
Meanwhile, if you have a finished novel, this is a must-have:
http://www.thewritershandbook.com/Invite.asp

See also 'creative writing' and 'publishing'.

TV
Notoriously hard to break into even for the talented and well-connected. The BBC website occasionally advertises internships and training jobs https://jobs.bbc.co.uk/fe/tpl_bbc01.asp and most independent production companies offer paid internships now too, e.g. Tiger Aspect, Cactus TV etc. Good screen writers can earn a decent living, though nothing like the riches of their brethren in Hollywood. And acting is for the birds - impossible to break into and harder still to make a living at. For actors over 30, there is only one place to start: http://www.thepoorschool.com/

FILM
Among the growth areas are animation and visual effects - since the Harry Potter franchise kick-started the London VFX business, many London companies compete successfully for big budget Hollywood dollars. Digital skills and training are a must, so check out the London Film School: http://www.lfs.org.uk/. For wannabe screenwriters and directors, have a look at: http://www.raindance.co.uk/site/

JOURNALISM
Traditional routes into journalism include the City University course, from which many Fleet St alumni have graduated: see http://www.city.ac.uk/journalism/. Local papers are still a good route in too. The website http://www.gorkana.com/uk/ is particularly useful for first jobs, but word-of-mouth is still the number one best route into Fleet Street, so get talking. Print media is however suffering from internet competition, and almost all newspapers have declining circulations. Magazines are in the same leaky boat, and no-one (except possibly the porn industry) has figured out a way to make money from the internet. Still, Fleet St soldiers on despite its problems and a good wordsmith can make a living. Public bodies like the BBC tend to be much more sheltered refuges from the chill winds of the private sector.