Hi,
I am a PHP developer for a large advertising agency in London. I've just started looking into freelancer.co.uk, so this is my first time using it. I've worked on many commercial websites, the work you require will be a simple job. I'd need from you either FTP login details (I'd advise you create a specific set for this work, and remove them after, for security), or the details of the method usually used to implement changes, that's something we can work out if you aren't sure.
Kind Regards,
Mike Payne