https://tech.newstatesman.com/security/uk-government-could-track-mobile-location-data-in-coronavirus-response

BT, owner of UK mobile operator EE, is in talks with the UK government about handing over its phone location and usage data for the purpose of monitoring whether coronavirus response measures like asking the public to stay at home are being adhered to, according to the Guardian. 

The newspaper reports that this will involve creating movement maps with anonymised data, meaning individuals could not be identified. Instead, it would be used to highlight patterns such as whether people were heeding government advice to avoid pubs and restaurants. (That a government mandated lockdown would prevent people from visiting such establishments, in addition to letting them claim insurance and stay solvent seems to have escaped Downing Street as of yet.)