Easyjet is the name of an airline. There doesn't seem to be an Easyjet Hotel. Do you mean the Easyhotel?
If so, this is a company that is owned by the Easyjet founder Stelios Haji-Ioannou. It uses the 'easyjet' name and is based on the same principles, of getting services to the customer at the lowest possible price. London is only one of its locations as it is a global company.
Like Easyjet, Easyhotel clearly markets itself as a budget company and as such, it doesn't pretend to offer luxury accommodation. Basically they offer smaller rooms in a range of locations, including very central ones such as Victoria. If you want to be well situated to visit London and don't mind relatively simple accommodation, you may like to look at an Easyhotel. Reviews are mixed as you can see here, but in any case it's probably worth taking a look.