The six major airports in the U.K. are London Heathrow, London Stansted, Aberdeen, Edinburgh, Glasgow and Southampton. The vast majority of air travel in the U.K. occurs at these airports.
The Department for Transport (DfT) establishes luggage safety regulations for air travelers in the U.K. As of September 2010, the DfT does not have a maximum size for carry-on luggage; however, specific airlines can set their own limits and routinely do. So check with your airline before deciding on a carry-on bag.
Directgov recommends that you arrive at the airport three hours in advance for extended international flights out of the U.K. They recommend that you arrive at the airport two hours in advance for international European flights and 90 minutes in advance for flights within the U.K. and Ireland.
Laptop computers and other small electrical items such as cell phones and hairdryers are permitted in your carry-on bag, but these items will be inspected at security prior to your boarding. Directgov offers an updated list of specific items that are and are not permitted either in your carry-on bag or your checked luggage.
The United Kingdom is home to six major airports and all of them are owned and operated by the British Airports Authority. The Civil Aviation Authority regulates all air travel in the U.K.