My husband and I will be staying 3 nights in London: May 23-26. I did a pretty exhaustive search looking for a centrally located hotel for less than $250 per night. The options are slim! The last time we were in London in May 2015 we stayed at an AirBnB in SoHo and loved the location, but the apartment had a few flaws (including very low water pressure in the shower) that we were disappointed with. So this time I found an "opening rate" at the Hotel Indigo on Leicester Square and decided to grab that.
We got a superior queen room for 175 GBP per night, including breakfast, wifi and late check out. The downside is we had to pay up front, so we can't change our minds now unless we're willing to throw way $750 :-( I had never heard of Hotel Indigo before but they have several other properties around London and the rest of the world that look very "boutique-y" nice and are well reviewed on Trip Advisor; I'm willing to take the risk.
It looks like the opening rate is still available on their website if anyone wants to check it out. I just did the search for the dates we'll be there and prices have bumped up a bit to 199 GBP per night for a standard room. They also have a less expensive room they call a Theatre Room: "Theatre rooms are designed to have no natural daylight" I prefer windows in my hotel room thanks...but if you don't care there's a cheaper option.