Key Worker

[Le Chat]

The company I work for are insisting that I am a key worker and that I must attend work, even though I am able to mainly do my job at home.
I work in Retirement Living but I am not a care or support worker and the scheme I work in is an independent living establishment.
I have a husband at home (now not working) who has MS and a 23yrs old son who had a heart attack in August, as yet cause unknown. So going home to vulnerable people. Alongside this, i was informed today that the son in law of one of my residents has been diagnosed (and is in hospital) with Covid 19. This resident and her daughter (wife of SIL) were in my office on Wednesday and in close enough contact.
Where do I stand on this? Is there a legal definition or is it defined by my employer?