while (<DATA>)
{
    if (( /^VAT/.../^DESCRIPTION/) && (!/^s*$/))
    {          
       next if /^VAT/;
       next if /^DESCRIPTION/;
       print;              #these are the address lines
       print "\n" if (/\w+\d \d/); #the trick is to see
                           #when address is done, eg a postal code
    }
}
__END__
prints:

Miss Carol Hocker
177 Elm Road,
Brighton
East Sussex
BN2 7HB

Mr Whatever 
177 Elm Road,
Brighton
East Sussex
BN2 7HB

__DATA__
Invoice

Invoice No:    C0331-2008    
Invoice Date:27/02/2008
VAT No:     679 7113 03


Miss Carol Hocker
177 Elm Road,
Brighton
East Sussex
BN2 7HB




DESCRIPTION

blah..blah

Invoice No:    C0331-2008    
Invoice Date:27/02/2008
VAT No:     679 999 03


Mr Whatever 
177 Elm Road,
Brighton
East Sussex
BN2 7HB

DESCRIPTION

...something here....