The legality is that you cannot visit someone's home in Birmingham, Solihull, or Sandwell from Tuesday. Also if you are from any of these areas yourself, you cannot visit someone's home in any part of the country. I hope that clears up the legal issue for Birmingham etc. If it classed as as a place of work, the law is different, but that opens up another can of worms, as it is place of work, social distancing needs to be adhered to.