Hotel accommodation can be expensive in London, and although it is possible to find cheap hotel rooms, there are some alternative options worth considering.
In the academic holidays, many of the universities and colleges will rent out their student accommodation at a fraction of hotel prices and they offer self-catering, so you can choose to eat out or make your own meals, or bed and breakfast. The standard and layout of the accommodation varies enormously so it's worth having a good look round before committing.
If it's not so much the cost but the hotels themselves that puts you off there are growing number of serviced apartments in London. These are similar to hotels in the quality of the rooms, but they are self-contained apartments so that you are free to do what you want when you want. This is of particular benefit to families with small children, who might not want to follow a hotel-type routine. The family is free to cook the meals that their children like and deal with their needs without having to wait for hotel staff to provide for them.