To add to StephanS's answer, "may be asked to take them to a police station within 7 days" is somewhat at the discretion of the police officer. If you can't produce them immediately and the police officer can't verify your licence/insurance status electronically then you are likely to be treated as driving without them. That includes immediate seizure of your car, and probably arrest if the officer can't verify your identity.
They can also seize a vehicle if they think it’s:
* being driven by someone who does not have a proper licence or insurance
The police advice states:
It is an offence not to produce your driving licence, certificate of
insurance and MOT certificate when requested to do so by a police
officer. However the usual action is that the police officer will
issue a HO/RT1/ (called a 'producer') requiring you to produce the
documents at a police station of your choice within 7 days.
And also states:
From a crime prevention point of view it is better never to leave your
driving documents in your car and produce them within the 7 day
A photo of a licence is also easily doctored (especially if it's only viewable on a phone) and may be treated as suspicious in inself. A good quality (black and white) photocopy, that is obviously a photocopy and not likely to be mistaken for an original document, is probably the best thing to carry if you do not want to carry your actual licence etc.