What do you mean by touring the London suburbs? If you mean attractions away from the very center, subways should work pretty well, but if you mean Cambridge, Bath, etc. I would suggest train service, which is frequent and often nonstop from the right station in central London. Nonlocal (medium and long distance) bus (called COACH, not bus, in British English) service is generally cheaper than trains, but can be slower. (If you do this, note that Victoria Coach Station is not the same as Victoria Bus Station in London!)