First things first... What is the relationship between you, the Driver and the Keeper? The reason ECP refused to engage with you is because until the Keeper transfers liability by providing them with your name and address, they do not have to engage with an unknown person who admits to being the driver.
As far as DCBL is concerned, you (or the Keeper in this instance) can safely ignore them. Debt recovery agents are powerless except to try and persuade the low-hanging fruit on the gullible tree to pay upon out of ignorance and fear. Never, ever, enter into communication with a useless debt collector.
All the Keeper has to do to transfer liability away from themself to you, the Driver, is to send a letter to ECP (by email is fine) according to whatever it says on the Notice to Keeper (NtK). Once the drivers name and a serviceable address has been provided, their liability ends and the driver is then solely liable.
Whoever ends up being the liable party can easily defend this. It will go all the way to a court claim which, with our advice, is easily defended and will in due course be struck out or discontinued.
The reason for the first question about the relationship between the Keeper and the Driver is try and understand why the Keeper would want to proverbially throw you, the driver, under the bus?