British are able to work up to 78 hours currently. However a recent vote was cast by the European Union to limit the maximum of working hours to 65 hours/week.
BUT all those numbers are maximums. The official normal working hours per week within the 27 countries of the European Union are 48 (see Directive 2003/88/EC). Therefore you shouldn't put more than 48 hours unless strictly justified and for a limited period of time.