The x-ray astronomy group at the University of Leicester is responsible for the development of two out of three of the focal plane cameras for the EPIC instrument on ESA's cornerstone mission XMM. CCDs are being developed in collaboration with EEV Ltd. of Chelmsford, UK, to perform the imaging spectroscopy at the prime focus of two of the XMM telescopes. The detectors require Fano-limited energy resolution and high detection efficiency over the 0.1 to 15 keV band. Devices are being constructed using high resistivity epitaxial silicon of 80 micrometer thickness, producing deep depletion, with an efficiency at the iron line (6.4 keV) of 75%. The low energy (less than 1 keV) x- ray performance is being maximized in the front-illumination devices by using novel 'open electrode' structures resulting in an efficiency of 25% at carbon-K (277 eV). This paper provides an update on the instrument concept and performance which is now entering the flight model build phase. The test results of the new custom CCD detectors are presented.