Ongoing assistance with web development

General information for the website: We are a waterpark
Kind of development: Customization of existing website
Description of every page/module: Due to a change in circumstance for our current dev we require ongoing support with our PHP website, hosted by Perch. We have a number of tasks that we need dealing with immediately.
Description of requirements/features: We have a mix of requirements from our email server playing up hugely, to needing our website reformatting for mobile, we need a perch upgrade so that we can add customer noted to our booking page.
Extra services needed: Customization, Optimization, Other
Extra notes: It is essentially that you are able to act promptly to requests as they come up. A lot of the amendments that we need to make are business critical so a speedy response time and actioning is one of the most significant requirements.