Day to day maintenance of Joomla driven websites - UK based developers only

We're a long established events and publishing company operating in B2B areas e.g. oil and gas, shipping. The 5 websites we maintain need frequent updating with new content, event information and so on. (For example, www.lngjournal.com). We employ a full time developer in house but our workload is far above what one person can handle. So we need a reliable and available helping hand (and backup for annual leave or illness).

Tasks will vary in their duration - we could have a job taking 5 minutes to complete, or one of several hours. Ideally we need a developer who is flexible in their billing and/or can batch up tasks towards the end of the day. Most of the work is quite mundane, but occasionally we might rely on your development skills.