Addison Lee owner drivers scheme, you can probably log on and off as you please
 
	OTS sends you e-mails, requesting quotes, which you can reject, or if you reply, they'll get back to you if they accept your quote.
 
	Crawfords and Brunel probably want you to work fixed shifts.
 
	Creative Cars probably ask you when you're available  to do jobs for them, they have lots of tv location work so usually need a number of cars in one go after filming.