Yep, you're right. That wasn't clear from the BBC story I read.
It seems that prepaid Mastercard can be used from tomorrow, and Electron will start attracting a fee from 1st January.
As far as I know, prepaid Mastercards are easier to get than Electron cards, as no identity or credit checking is required, but the disadvantages are that you will almost always have an unused balance sitting on the card, and many providers charge a fee when making a purchase or topping up the balance.