Yes you are free to cancel, up to the point of entering your pin. However, you may lose the money on any extras you have paid for at that stage, so just make sure, it’s the right car for you, or you can argue your case. deposits should be ok, and should definitely be refunded, if delivery is taking an unreasonable time, eg. you were told Dec, but now July, you would be within your normal consumer rights to cancel without penalty.