Maritime Underwater Future Capability (MUFC) is the designation for UK Ministry of Defence studies to replace the Royal Navy's Trafalgar class submarines and follow on from the Astute class.
The MUFC project started as the Future Attack Submarine (FASM), which envisaged the Astute class replacing the Swiftsure class submarines and FASM replacing the Trafalgar class. In 2001 FASM was cancelled and replaced by MUFC.
The MUFC could result in an entirely new design but is more likely to be a development of the Astute class submarines for cost reasons. Reports (e.g. Defense News) have suggested that the MUFC studies may result in a single class of multi-role submarines to replace the Trafalgar class, Vanguard class SSBNs and eventually the Astute class. This would require a submarine capable of launching conventional land attack missiles, some form of nuclear missile (ICBM or tactical nuclear missile) as well as conventional submarine munitions including mines and torpedoes.
MUFC source (2006): Wikipedia
Design Concept Engineers - Submarines (Derby, UK)
Trafalgar-class submarine (Wikipedia)