It must include all your vital details....name, current London address, age, marital status, nationality, visa details (optional), education, and most importantly--a daytime phone number! Sometimes a reliable friend with an answering machine, or an answering service, or pager, will do. 

It is best to list only your most recent & relevant jobs, you don't necessarily need to list every single job you've ever had.  You should give your employment history in chronological order from your most recent to your earliest positions. Describe the positions you held, the duties you performed, the skills you acquired and the length of employment at these particular jobs. If you have any computer experience, no matter how small, it is advisable to put it down as its a very important skill to have. You can also include your hobbies/interests as well.

If you don't have a CV ready, you can easily have one made for you at many places in London. They are professionally prepared and cost around £15. You can do it yourself at many of the computer shops around London like Input/Output centres, or Declare. Usually you pay £5 an hour to use the computer, which includes internet access for those in need of email.

Most agencies prefer that you fax your CV to them before the interview. Some may not schedule an interview until they have seen your CV. You can also send out your CV by post to any interested companies, agencies, etc before you arrive in England. Your local library in your home country may have addresses of businesses in the UK. Either way, a CV is the most important thing to have once you arrive in London.