User Interface Designers (UI Designer) differ from UX Designers in that they are responsible for taking the UX outputs (wireframes etc.) and concentrate on how best to layout the design for the platform/site.
They are in charge of designing each screen or page a user interacts with and ensuring that this delivers the best possible experience. Just like graphic designers, UI Designers have a real understanding of layout and typography albeit with a specialisation in digital channels / platforms.
Given the popularity of mobile devices, both UX and UI candidates must have experience in creating effective user experience and journeys across all desktop, mobile and tablet devices – responsive, cross-browser design experience is therefore essential. The boundary between UI and UX designers is fairly blurred and it is not uncommon for companies to opt to combine these roles.
Salary wise outside of London the role generally pays between £30,000 to £45,000 depending on regional variance and level of experience.