LDC
On est tous des pangolins
I'd have an app, if given a free phone with free contract. I'd isolate, but I'm doing that already. If a cold caller rings up and knows me by the alias i give the app, then I may listen to their instruction, but I'll want detail. If I caught the virus I'd want to drive 250 miles to a holiday home to isolate properly.
They'll get detail as someone you almost certainly know will have told them where they had close contact with you, for how long, what type, and then passed your name and contact details on to T&T.