Do I have to have both parts (paper & photocard) driving licences - I only have the paper one ?

It is good to have both the green paper counterpart and the photocard too. The counterpart shows any endorsements you have received and the credit sized card displays a clear picture of you.

You can use the photocard where photo identification is required. For example, some airlines accepts the photocard driving licence if you don't have your passport for domestic flights within the UK. Or you can use it to open a bank account. So it comes really handy.

When hiring a vehicle, usually the rental company would want to see both parts of the licence. This allows them to confirm your identity and make sure you're not banned or pose a great risk to them. Some car hire companies may accept to give you a car if you don't have both parts but may require you to either fill in an indemnity form or charge you extra to check with DVLA about your endorsements.

It is to be noted also that it's through the counterpart that you can make changes to your driving licence, eg change of address or name and it is an offence to have outdated details on your driving licence.

So with all the benefits of having both bits, there's also an obligation to retain them as well.