Also, I think you're saying that there should be more debugging output from the 2 step method you suggest. There is, which I believe suggests that the xpath is wrong (I got it from firebug's inspect element followed by copy xpath). The error I got is:

No elements found for '//*[@id="submit"]' at scrape line 15
No elements found for Button with name '' at scrape line 16
Can't call method "__click" on an undefined value at /home/tom/perl5/l
+ib/perl5/WWW/Mechanize/Firefox.pm line 1924, <DATA> line 1.
[download]

The button seems to be added only "later" on, after even DOMContentLoaded has fired. I get your script to work consistently by using sleep 1 to give the page more time to construct itself:

use strict;
use warnings;
#use local::lib;
use WWW::Mechanize::Firefox;
warn $WWW::Mechanize::Firefox::VERSION;

my $mech = WWW::Mechanize::Firefox->new(
    autoclose => 0,
    autodie => 1,
);
$mech->get('http://www.rightmove.co.uk/');
# Filling in and submitting the first forms works:
$mech->submit_form(
                   with_fields => {
                                   searchLocation => 'N1',
                                  }
                  );

sleep 1; # give the page more time
$mech->click({xpath => '//*[@id="submit"]'});
[download]

To make this truely robust, you would need to wait (always with a timeout!) until the search button becomes visible:

my $retries = 10;
while ($retries-- and ! $mech->is_visible( xpath => '//*[@id="submit"]
+' )) {
      sleep 1;
};
die "Timeout" unless $retries;
[download]

Works perfectly! I'll go with your retry and countdown method. Thank you very much for both the module WWW::Mechanize::Firefox and the support.

Dear Corion, I have a doubt on this thread. Can you pls suggest a way?

Is there a provision to pass a string to it like below,

 my $Pager = "submit";

my $find_button = $mech->xpath('//*[@id="$Pager"]', single => 1 );
$mech->click( $find_button );
[download]

Its not getting me through! Giving an error like 'NO elements found'

Thanks in advance.