I agree with the suggestion of XP-2+. If you take some time NOW to learn B&W, shooting and developing, then maybe a real B&W film.(posted 8546 days ago)I budget 2 rolls per day, rounded up to an even 5 or 10 depending on the length of a trip. I prefer to bring film home rather than worrying about running out. Of course, in London you will be able to buy just about any film there is, but not all places are so convenient.
You do need to test, but in general a light yellow filter brings up the contrast under flat lighting.