The following national train companies operate in the UK:
Arriva Trains Wales
Operates trains between London, Birmingham, High Wycombe and Aylesbury.
London Docklands Light Railway
Operates trains from the Tower of London to Canary Wharf and Isle of Dogs.
East Coast Railway
Operates trains from London (Kings Cross) to the North east of England and Scotland. Travelling between London, Leeds, York, Newcastle, Edinburgh etc.
East Midlands Trains
Operates trains to London and stations throughout the East Midlands, including Leicester, Derby, Sheffield, Nottingham and Lincoln.
Operates trains from London Waterloo to: Antwerpen, Bruges, Ghent, Brussels, Namur, Lille, Paris, Disneyland Paris and Ski Trains.
Operates trains between London Paddington, South Wales, The Cotswolds and the West of England.
First TransPennine Express
Operates trains in the North of England, from Leeds to Liverpool, Manchester to Middlesbrough etc.
Operates trains between Gatwick Airport and London Victoria Railway Stations.
Operates trains from Heathrow to London Paddington, every 15 minutes.
Direct London to Hull service.
Operates train services through the midlands from London to Birmingham and Liverpool.
London's underground railway - The Tube.
National Express East Anglia
Operates train services in East Anglia.
Operates local and inter-regional train services in the North and North East of England.
Operating local and long distance services around Scotland. Also operates the Caledonian Sleeper services between London and Scotland.
South West Trains
Operates trains from London Waterloo to the South West.
Operates train services in south London, between central London and the South coast, through East and West Sussex, Surrey and also parts of Kent and Hampshire.
Operates train shuttle service to Stanstead Airport.
Operates train services for destinations up and down the country, from London Euston to Glasgow and Edinburgh.