Hi,
Just to let you know, anything that has a transformer between the power point and the item should be fine. For example, camera chargers, phone chargers, laptop supplies etc. The transformers convert the voltage into the correct level for that component.
As previously mentioned, the domestic supply is 110v and the UK is 240V so UK equipment should not be affected. US electrical kit will not however work in the UK, you would probably pop the fuses.
Hair driers have a heat element which requires the full 240 volts to work at its best. The lower voltage will mean that the element will take a lot longer to heat up and the fan speed will be reduced.
My girlfriend says that the hair driers in the hotel rooms are as good as when she attempted to use her UK hairdrier.
The adapters are available all over the place, Argos is particularly cheap, but I am sure I only paid £3 at the airport for one. Definitley consider at least 2.