Whilst I was aware of the plans to "retire" the paper counterpart, I was unaware of the requirement to generate a "code" three days before you intend to hire a car.

Whilst I suspect, in practice, you would never be asked for said code (after all, I have never been asked for both parts of my license for any of the multitude of car rentals I have made throughout the world - despite being told each time I "need" to bring it), it doesn't hurt to familiarise yourself with the apparent requirement:-

http://www.bbc.co.uk/news/business-32481382

According to a DVLA "spokesperson", this has been widely publicised for months. However, I, and probably most on here will not have heard a thing about logging in to a website to acquire any 'code' of any sorts....because there has been ZERO information released to the public about it! Surprise surprise!! (Another former Government department with 'failure' stamped all over it!!!) Bring back the good old DVLC, not this Labour-designed/run shower of incompetence. Rant (far from) over!!!!  Foraging near Gaydon....
——————————————
MY13 HSE Lux SD4, Baltic Blue - current, 30,000> miles without fault
MY12 HSE 2.2 SD4, Sumatra Black - gone after 10 months/43,000 fault-free miles