Britain has a quite extensive network of passenger trains, with most places being no more than 20 miles from a train station. Most routes have a train at least once an hour, except in the most rural areas.
Despite the division of the network between some 25 private operators, it is still possible to buy a ticket from any station to any other station, irrespective of who runs the train(s) between them. For many journeys, a wide range of ticket types is available, depending on how far in advance you are buying, and what restrictions you will accept on your choice of train. Some types of ticket are not valid at particular times of day, or on particular trains.
When a train journey involves a connection across London (between different terminal stations), the ticket is usually valid on the London Underground (metro) - it is not usually necessary to buy a separate London Underground ticket.
Unlike the situation in many European countries, the train timetables (schedules) can be very different at weekends, compared to weekdays (Monday to Friday). You should ensure that you check times for the correct day. The situation, particularly at weekends, can also be complicated by the closure of sections of railway for engineering works. Trains will be replaced with coaches or buses, but these are likely to be slower.
In most cases, it is necessary to travel from the airport to central London, with some or all of this journey by London Underground (metro).
There are train services from several different London stations to Birmingham:
There are two ways to travel from Heathrow airport to Euston station. The Piccadilly line of London Underground (dark blue on the Underground map) provides a very frequent service from Heathrow to central London. To reach Euston, you should change onto the Victoria line (light blue) at Green Park. The typical journey time from Heathrow to Euston is about an hour.
An alternative Underground route to Euston is to change twice: first onto the District line (green) at Hammersmith, and then onto the Victoria line (light blue) at Victoria. The typical journey time from Heathrow to Euston is about an hour and a quarter.
Alternatively, the "Heathrow Express" rail service runs to Paddington station every 15 minutes, taking 15-20 minutes. It is, however, much more expensive than the Underground. From Paddington, you should take the Circle line (yellow on the Underground map) to Euston Square, and then follow the signs to walk to Euston station.
To avoid the short walk in the above route take the Bakerloo line (brown on the Underground map) to Oxford Circus, and then the Victoria line (light blue) to Euston station. It is also possible to travel from Paddington station to Birmingham by train (see above).
Gatwick airport has its own railway station; tickets for the train journey to Birmingham should include the connection across London by Underground. From Gatwick, trains run to Victoria station in London, at least once every 15 minutes, with a journey time of 30 minutes. Once at Victoria station, go down to the Underground station, and take the Victoria line (light blue on the Underground map) to Euston.
There are also trains from Gatwick once an hour to Watford Junction, north of London, where some of the London - Birmingham trains call. This route is slower, but may be preferable if you have heavy or cumbersome luggage.
Stansted airport also has its own railway station. Trains run through to Birmingham once an hour, taking a little over 3 hours. It is also possible to travel via London, but this is more expensive.
There is a through train from Glasgow Central station to Birmingham New Street station usually every 2 hours, with connecting trains available in between. The journey takes about 4 hours.
BAA (Heathrow, Gatwick, Stansted): www.baa.co.uk
National Rail Enquiries Online (timetables, travel disruptions): www.nationalrail.co.uk
DB / Hafas: bahn.hafas.de/bin/query.exe/en (better timetable enquiry, covering the whole of Europe, but not updated for engineering works)
London Underground: www.tfl.gov.uk/tube
Qjump (rail ticket prices and sales): www.qjump.co.uk (registration required)
With thanks to Mark Waller for the research and writing the text.