Siemens Desiro

United Kingdom
Siemens uses the name Desiro UK for the DMU and EMU trains operated by various United Kingdom train operators. These trains have a completely different design to the lighter Desiro Classic variant. The trainsets have modern equipment such as toilet waste retention tanks, ergonomic seats, and automated information displays and spoken announcements. All the units are owned by rolling stock operating companies (ROSCOs), apart from the 360/2s which are owned by BAA for the Heathrow Express and Heathrow Connect services. The 350/1, 360/1, 444 and 450 electric units are owned by Angel Trains, the Class 350/2s are owned by Porterbrook and Class 380s are owned by HSBC Rail. The diesel units are owned by HSBC Rail. Angel, Porterbrook & HSBC Rail lease their units to the train operators.

EMUs
The first electric Desiro UK units were ordered by South West Trains for both short and long distance service out of Waterloo station to Alton, Basingstoke and the Hampshire/Dorset coast. They became two different classes, both of which use the 750V DC third-rail power supply. One hundred and ten Class 450 four-car units for commuter services which entered service in 2003. Forty five Class 444 five-car units for long-distance inter-city services entered service in 2004. An additional order for a further seventeen Class 450 units was placed with the trains being in service by late 2006/early 2007.

Former East Anglia train operator First Great Eastern acquired 21 Class 360 four-car units which operated from 25 kV overhead electrical supply for services from London Liverpool Street to Clacton-on-Sea/Walton-on-the-Naze, Harwich and Ipswich. The vehicles entered service in 2003.

For the stopping service between London Paddington and Heathrow Airport called Heathrow Connect five Class 360 five-car units were acquired and entered service in June 2005.

As part of the modernisation of the West Coast Main Line the former Strategic Rail Authority ordered thirty Class 350 dual voltage sets for use on stopping services. They are operated by London Midland. These units were originally ordered as Class 450 third-rail units for South West Trains, but following a review by the Strategic Rail Authority they were diverted to the West Coast main line. The dual-voltage capability has only been used in service on temporary loan to Southern on Milton Keynes Central - East Croydon services whilst covering for a shortfall of Southern class 377 Electrostar units. The units have been praised for their air conditioning, accessibility and performance, but criticised for their comfort (newer units have 3+2 seating). Thirty Class 350/1 four-car units entered service in 2005, and in 2008/9 a further thirty seven Class 350/2 four-car units entered service.

On 11 July 2008, First ScotRail ordered a number of Class 380 EMUs for delivery in 2010. The order was for 22 three-car and 16 four-car units. First enter service began 8 December 2010. Inverclyde Line, Ayrshire Coast Line of the Class 318, Class 334 "Juniper" was introduced to replace the fleet, and the North Berwick line Class 322 trains have been replaced.

DMUs
To fulfil their franchise commitment, First TransPennine Express ordered the first diesel variant of the Desiro UK for use on its inter-city services across the north of England and over the border in southern Scotland. 51 three-car units classed as Class 185 entered service in 2006.

Desiro City
Desiro City is a planned high-capacity commuter EMU for the UK market building on the Desiro UK and Desiro Main Line, with a reduction in weight and energy use and 'fly-by-wire' controls.

A consortium led by Siemens is preferred bidder for the Thameslink rolling stock programme. 1140 dual-system 750 V DC/25 kV AC Desiro City vehicles will be supplied, suitable for use with the Thameslink ETCS Level 2 signalling. They will operate in either 8 or 12-car formations. The Desiro City design has also been put forward for the Crossrail rolling stock contract; Siemens was placed on the tender shortlist in 2011 with five other manufacturers.