Just a few quotes from the current information on the Foreign & Commonwealth Office website:
"There is a high threat from terrorism. Although security is tight throughout the country, especially in resort areas, there remains a high risk of attacks which could be indiscriminate, including in public places frequented by foreigners. Following French military intervention in Mali, there is a possibility of retaliatory attacks targeting Western interests in the region. You should be vigilant"
"Demonstrations happen regularly across Egypt, often on Fridays. Some have been violent and resulted in deaths. Police may use tear gas for crowd control. You should avoid all demonstrations and large gatherings. If you become aware of any nearby protests, leave the area immediately."
"Reports of cases of sexual assault against British nationals have increased during and since the unrest of early 2011. In 2011, the FCO handled 20 cases of sexual assault and 6 cases of rape. Some assaults were against minors. Many occurred in what were considered to be safe places such as hotels. Assaults have occurred in taxis and on microbuses. If you are travelling on a microbus, avoid being the last passenger left on the bus. Women should take extra care when travelling alone"
Lot more here:
http://www.fco.gov.uk/en/travel-and-living-abroad/travel-advice-by-country/middle-east-north-africa/egypt