I have created the following formula to try and get multiple parameters selected to show:
if (join({?area},", ")) = "2" then "Bournemouth" else
if (join({?area},", ")) = "3" then "Poole" else
if (join({?area},", ")) = "51" then "Beaminster" else
if (join({?area},", ")) = "52" then "Bridport"...