Seeking advice.

Hi, I will be traveling to London (arriving at LHR) for a class trip. I dont want to leave on the day they suggested to get into London on the 28th of May, I want to arrive a day earlier. (The tickets there are expensive on the dates rhey suggested) Anywho, I've never been and I dont want to book an expensive hotel room just to stay there one night. I was wondering what are some nice options I can book for a day stay that aren't far from the airport while I wait for my professor and classmates to arrive on the 28th?

Its my first time traveling to London. So please be nice lol 😆