I tend to stay for longer periods so I book an airbnb room. But when I do book a hotel, it's usually a Travelodge or Premier Inn. They are modern and have everything you need and are so much more inexpensive than any other major hotel prices I have actually ever seen in any other city! The more inexpensive ones are outside of the city centre (West End) but the tube and train system here is so good you really don't mind (usually not more than a 25 minute ride)! Plus, it's fun to experience the gorgeous London neighborhoods a lot of these hotels are situated in.