Assign area to postcode from multiple arrays function

Try such array formula *in B1:

Formula:

=IFERROR(OFFSET(Sheet2!$A$1,0,MAX((A1=Sheet2!$A$2:$C$5)*COLUMN(Sheet2!$A$1:$C$1))-1),"No sector")

*...confirmed by pressing CTRL+SHIFT+ENTER to activate the array, not just ENTER. You will know the array is active when you see curly braces { } appear around your formula. If you do not CTRL+SHIFT+ENTER you will get an error or a clearly incorrect answer. Press F2 on that cell and try again.