I need to write a marketing plan for one facility within a care company which is underperforming compared to the others. One reason is due to poor branding and attracting the wrong clients. What elements should I include to denote the rebranding of the centre and potentially alter the target market in peoples minds, and increase its revenue?
Your question is rather generalized and vague as to what aspects you are looking for.
Going solely by what you have written in your initial question, I see that you have a pretty good grasp of the problem. Restate your main question, even to yourself, and be as specific as possible. What do you mean by elements and subsections? The more specific you are, the more you will find your own answers.
Generally, your marketing strategy should state your unit's mission and objectives, your target market (a description of user types, model user, demographics, income, geographic area, education, age, status, etc.), budget, and the four Ps (Price, Product, Place, Promotion) or your marketing mix.
Answer the following questions: What is wrong with your current branding? What are the right and wrong clients? How will you reach the right clients? What is your message? What networks (friends, referrals) do your ideal clients or users use to reach you? Is it easier to reach these networks than the general public.
Once you have done some basic work on these issues, you can determine, along with your budget, what your appropriate advertising and promotion efforts should become (e.g. press release, radio, posters, logo, icons, slogan, news article, letter to the editor, banners, fliers, website, email lists, newsletter, face-to-face, etc.).
Keep in mind, the target of your message may differ from your target market. If your clientele reaches you mainly through referrals, you may want to target those who refer, rather than the ultimate users. This can be both cheaper and more effective.