Will not be released from work if Covid19 affects workplace according to employer

Hello,

I need advice and I’m sorry about being so vague on the details as I’d like to remain anonymous in case my boss reads this.

I work in a small business- there are five of us spot across two small rooms...including the boss.
We work in an area where vulnerable people come into our shop -there is face-to-face interaction for goods and services.

His business is doing well off the back of this global pandemic; I’m grateful for the job security and empathize with others on here who are not so fortunate.

His nephew worked a day in the shop 6 days ago and we were informed this morning he’s waiting to be tested for Covid-19. Our employer has stipulated that we are not to go home and self-isolate - even if one of our members falls ill.

He’s a bit of a micromanager and I think a bit clueless because this cannot be right.

In the event of a positive test result, could you clarify my rights here before I argue my case with him?

Thank you