How to find voluntary work that would help an actor to get a foot in the door
There are always workshops and opportunities online. These can be found through CCP, Twitter, Facebook pages, artjobs.com and through searching websites of companies and theatres. The best way to keep track of what's going on is to join mailing lists, or to offer your voluntary services via email to the places you want to work.
A lot of companies are looking for volunteer performers or ushers, and this is a great way to make yourself known to the people you want to work with. Don't be afraid to contact the companies you are interested in offering to help out, or asking to sit in on their rehearsals.
Short films are always a good way of getting experience and footage for your show-reel. A lot of universities cast via CCP.
Edinburgh Fringe and Brighton Festival Fringe look for volunteers every year to help out around the festivals. Just being at these events can be an invaluable way of networking and learning more about the industry.
If you're 16-25 there is so much going on in London that you can involve yourself in. A lot of theatres have youth theatres or 16-25 schemes that provide you with training, professional looking credits and great networking opportunities. Look around your local theatres, with some you need to be in the right catchment area to join so this is a good place to start.
Every time you volunteer you will meet someone new who works in the industry, and people are always happy to accept extra help in an industry that is short of funding, and with any luck they will remember you and keep your details for the next time they are looking for volunteers or indeed actors. Be careful not to do too much, remember that you still need to earn money to live off and that some people will take advantage of your willingness to work for free. Other than that just keep your eyes and ears open, don't be afraid to put yourself out there and take every opportunity once, you never know where it might lead.