The site is vulnerable, because your Joomla version is outdated.
You should update your CMS!
See:
http://sitecheck.sucuri.net/scanner/?scan=http%3A%2F%2Fnanogate.co.uk%2FJoomla Version 1.5.18 to 1.5.26 for: htxp://nanogate.co.uk//language/en-GB/en-GB.ini
Joomla version outdated: Upgrade required.
Joomla Version
1.5
Found in META Generator Tag
The following modules were detected from the HTML source of the Joomla front page.
No modules were found passively in HTML source
The following components were detected from the HTML source of the Joomla front page.
No components were found passively in HTML source
The following plugins were detected from the HTML source of the Joomla front page.
No plugins were found passively in HTML source
Google safe browse check
PASSED
Google finds the site to be free of malware
Server: Apache/2.4.9 (Unix)
X-Powered-By: PHP/5.2.17
IP Address: 79.170.44.141
Provider: HEART INTERNET LTD
Country: GB
The IP had a history of PHISHing!
polonus