I think that you're out of luck:
According to Wikipedia (which is usually extremely reliable for up-to-date airport information) the only direct scheduled flights from the UK are with Bmi from Manchester (service ends 25th April) and Virgin Atlantic from Gatwick.
The only charter flights from the UK are with Thomas Cook, from Belfast, Glasgow & Manchester:
http://en.wikipedia.org/wiki/McCarran_Internat ional_Airport
The McCarran Airport website doesn't carry a list of destinations served from the airport but the list of operators using the airport seems to be consistent with the information above:
http://www.mccarran.com/airlines.asp
Chris