Originally Posted by yying

From my experience in Japan (10+ journeys), hotels are generally happy to store your luggage on the same day you check-in or check-out, so there is absolutely no problem to leave your luggage after checking out from hotel in Tokyo, enjoy the final day of the trip then return and collect the luggage from the hotel at a later time the same day. There are also plenty of lockers are major train stations in Japan which can fit in large bags.

I've not stayed in a hotel in London personally, but I'd assume the same from what I experienced in other EU countries.