Enabling GZIP compression on magento/siteground

Experts,

I have a site hosted with siteground:
http://www.chic-osity.co.uk

I have followed steps provided by the hosting company to enable GZIP compression, namely adding the block below to .htaccess

<IfModule mod_gzip.c>
mod_gzip_static_suffix .gz
AddEncoding gzip .gz
AddEncoding gzip .gzip
mod_gzip_on YES
mod_gzip_handle_methods GET
mod_gzip_temp_dir /tmp
mod_gzip_can_negotiate Yes
mod_gzip_dechunk Yes
mod_gzip_send_vary On
mod_gzip_update_static No
mod_gzip_keep_workfiles No
mod_gzip_minimum_file_size 250
mod_gzip_maximum_file_size 1048576
mod_gzip_maximum_inmem_size 60000
mod_gzip_min_http 1000
mod_gzip_item_exclude reqheader "User-agent: Mozilla/4.0[678]"
mod_gzip_item_exclude file .js$
mod_gzip_item_exclude file .css$
mod_gzip_item_exclude mime ^application/pdf$
mod_gzip_item_exclude mime ^image/
mod_gzip_item_exclude mime ^application/x-javascript$
mod_gzip_item_include mime ^text/.*
mod_gzip_item_include file .html$
mod_gzip_item_include file .pl$
mod_gzip_item_include file .cgi$
mod_gzip_item_include handler ^cgi-script$
mod_gzip_item_include mime ^httpd/unix-directory$
mod_gzip_item_include mime ^application/postscript$
</IfModule>

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Then adding the following to the top of index.php:

<?php if (substr_count($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip')) ob_start("ob_gzhandler"); else ob_start(); ?>

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They advise that gzip is working, because the following site states it to be the case:
http://www.whatsmyip.org/http-compression-test/

However, when i load the page in firebug, then perform a page speed analysis, it states that it is not enabled.

I am keen to do everything that i can to optimize the sites performance and increase load time, therefore any suggestion on how to do this would be greatly apprciated.

Regards
Easynow