So, you're a writer.

Might you need a agent?

You don't need an agent but, it would be good to have one. It also depends on what industry you are working in. For example in the past most authors have tried to get an agent who would then try and get your book published. This has now changed with the advent of e-books. As you can now self publish.. which gets you going its then down to you to create the noise that will get people to want to down load your book.
However most Actors do need an agent as agents are on the lost of casting for the film and TV companies. You can be lucky and send your CV around and if the times right a film or TV company could invite you in for an audition .. but that is very much down to luck. Where an agent would have a system in pace to get your details out the casting people and hopefully get you in front of them. 

What the hell is an agent? 

An agent is someone who acts on your behalf. They will know the casting or publishing agents and should have an idea in advance as to what is required etc.
So they get you the jobs or that trilogy book deal ..!
The will also if you are lucky enough to get select for a role or to be published negotiate your fees etc. They of course take a cut / % of this fee which can be large.

Do you want one?

Yes.
In an idea world an agent would do all the above which would allow me to spend my time being create and writing my master piece. A lot of creative people are just that and when it comes to deal making they cry away or can get stitched up. So an agent should be harden to this and get a good deal.

Either you or your agent need to a commissioning editor at the BBC.

Find a name of a BBC commissioning editor?

Lindsay Bradbury - Commissioning Editor, Factual Features & Formats and Factual Commissioning Executive for Northern Ireland.

What the hell do they do?

Commissioning editors is in charge of commissioning programs. 
He or she will have a specific guide line ti work or set area that they work in.

For example Lindsay Bradbury featured above is a Factual Commissioning editor. So her brief will be to look for and find News / real life based programs for the BBC. She is part of the the Features team. So that could be starting a new project from internal ideas or looking for ideas sent in to her from outside.

What's e-commissioning?

e-Commissioning an on-line automated system that allows writers / producers to submit ideas for programs / films directly to the commission company.
This could be done by way of a PDF or powerpoint presentation submitted via the internet to the companies e-commissioning system.

Heres is a link that you can use to submit ideas etc to the BBC - http://www.bbc.co.uk/commissioning/tv/pitching-ideas/e-commissioning.shtml

The BBC aren't interested. But maybe Warner Brothers are?

If you were going to get your Single Camera Drama adapted into a movie at Warner Brothers, who would decide whether it happens?

Once submitted there will be a few vetting systems in place before any one with real power gets to look at it. A  producer will eventually get your idea and he or she will decide if your idea will become a movie.

How does stuff at Warner Brothers get green-lit?

If a pitch succeeds, a film receives a "green light", meaning someone offers financial backing: typically a major film studio, film council, or independent investor.
It means a producer likes your idea enough to put his or her name to it and talk to the money people and try to get funding. Once that is in place then their work begins.

Warner Brothers don't buy it, but an independent film company do.

How involved might you be from this point? Find a story about what happens to a writer during development and production.

I think that if a major film company buys the idea once they have it you some what say good bye to it.. and just take the money. If a small Independent picks up your idea you have a much better chance of being involved all of the way. As they could values your creative input and ideas.

The independent company are worried about errors & Omissions insurance on your script. What is it, and why might they need it?

Errors & Omissions insurance which is a USA name for Professional liability insurance (PLI) which is there to protect the film company / its people in case it / they gets sued in anyway for neglect / financial loss and errors etc as its name implies. It does not cover things like criminal prosecutions murder etc. PLI is normally require by law in some areas to make sure people / companies are covered. Its cost can vary in size depending on how the insurance company see the risk involved.