?50 for a cab is about right, you might get ?40 if you phone around, but with a flight to catch (and if your company is paying) then its worth paying for a reliable company. This will usually be the quickest route, about an hour door to door if you are leaving between 5-6am to get an early business flight somewhere. Alternative route via public transport for you from Barry Road is No 12 bus down to Peckham Rye station, train to victoria, tube to paddington, which will take about an hour, not including heathrow express/connect.