Design Website Mockups for Wordpress sites, possible long term

I manage a variety of projects and have staff to cover them, however there is sometimes overflow that we can't handle. I am seeking an individual or firm that can handle a range of design projects to cover that overflow. Most are Wordpress projects, things like taking a creative brief and wireframes to build design comps. You can expect the first round to be to present two to three concepts, then two rounds of review. User Experience is usually defined by me to some degree before bringing you in. Your output will be the final comps as high-res images and the PSD with all layers. You will bid on projects from details I am provided from initial contact, then again when I refine the requirements with the client. This bid is for a specific project that is a good example of the project types I get. If we work well together on this one we can build a long term relationship. <THIS PROJECT> -Custom Wordpress site, client hosted -Subscription model site with 5 levels of subscriber that allow access to 5 different levels of content. -Total content of site ~500,000 words -Discussion forums required, access restricted based on subscriber level. -Custom page templates, 5-8 page types -Fully responsive -Assume some additional design tweaking as development begins and a final check once the site is in QA to assure design is properly represented. Please provide your total anticipated hours as well as cost, and assumptions made to get to that number. Designers from the UK, Australia and USA preferred.