Harry Potter Studio Tour- London Questions

Has anyone ever done this? We're going on a large European tour, with a stop in London, and this was on many of our to-do lists. But I'm a novice to all things international/European travel, so I'm very out of my element here. If anyone can give ideas, tips, or even basics (where to get tickets, transpiration, what to expect, etc.) that would be a lifesaver, I would even consider this a lift debt, that I will try to pay it back/forward!!