The 35 Birkin holds way more than a Paddington. And with your height, you could also carry off a 40 quite well, I would think. It just depends on how big/heavy a bag you want to carry. Since you're in London, you should try to go to the Hermes store and ask to see the leather book as well. I would also ask if there are any Birkins in the store so you could hold one and see how the size works with your frame. (Sometimes they have bags that are used strictly for media and photography purposes...)