We need a Magento website Manager

We have a magento website (which is probably too big and complicated for what we need) however, Fasthosts is where it's hosted and we basically need someone who is contactable by email and phone to make changes and updates to the site. At the moment we need a banner put up, as well as a few changed around, and who can assist us with any backend questions/issues that might come up.
Artwork for new banners keeping with our brand would also be helpful but not essential as we do have a designer worst ways. We just need someone to do the visual changes to the site that we can't do. Knowledge of SEO might as well be helpful - we've taken our eye of the ball re the website and need help getting back on track, from someone reliable, affordable and contactable! This is ongoing, and intermittent work, shouldn't ever be more than a couple of hours a week I would expect. You can charge us per job ideally.