Good for you finding a solution. As for shift levers, placing them on the stem (handlebar pole) isn't a great location. The best solution would be a pair of thumb shifters mounted within reach of your handgrips. They can be reached without taking your hands off the grips. You had great help at the London Bike Kitchen no question. Maybe you should go back there and see if they can help you find a pair of thumb shifters. The best ones I have ever used were Suntour Power shifters, the design is brilliant and intuitive. A pair of those shifters mounted right where you could operate them without taking your hands off the bars would be at least 10 times better than a stem mounted shifter