If you had paperwork to prove the car was your only way of earning money they would probably have left you the vehicle.
If you had spoken to them and tried to make arrangements they would have forwarded your offer to the client, who would have made the decision, not the agents.
They hold the car for 14 days before putting it into auction. They will have told you that, but, from your post, I am assuming you either weren't listening or did not understand that. So ring them and start a dialogue, now!
Tessie that is not true, they can, the explanation is in a post above yours
www.citizensadvice.org.uk/debt-and-money/action-your-creditor-can-take/bailiffs/what-bailiffs-can-take/check-what-bailiffs-can-take/
As others have said, you have to ignore a lot of letters to get the bailiffs at your door, you have to ignore a lot of attempts at communication to get to this stage. Whatever your reason for this, the worst has now happened. So, head out of the sand, start putting it right, as much as is possible.
CAB, StepChange and others can help.
Good luck