From Hong Kong to London (UK), several direct flights are available daily which are respectively operated by British Airways, Qantas Airways, Finnair and so on. And there is no direct flight operated by Aeroflot on the route. If you need to transit at Moscow, you could choose a flight to Moscow first and then take one flight to London. About visa, it is learned that no visa is required for Hong Kong common passport Holders to enter in Russia less than 14 days. For sure, you are suggested to consult the Russia Embassy in Hong Kong for details.