You're not adding 35 minutes to your journey time. You yourself stated you arrived at T5 just before 1900 for a 1930 flight. If you normally find yourself at the airport 30 minutes before departure then getting yourself there 35 minutes before departure is no great shakes. Thats a piddling 5 minutes extra. Frankly I don't think anyone is too busy that they can't get to an airport 5 minutes earlier.