Question: The head office of Stagecoach Merseyside & South Lancashire was formed following a merger containing the regional bus operator based in which Northwest England town?

Context paragraphs:
TM Travel: TM Travel is a bus operator based in Halfway, Sheffield, operating bus services in South Yorkshire and Derbyshire.  Founded in 1995 as a family-owned operation with one bus, by March 2008 it had expanded to become the largest independent operator in Derbyshire.  The company was taken over by the Wellglade Group in January 2010, and as of August 2016 operate more than 70 buses.

Stagecoach in Norfolk: Stagecoach in Norfolk (formerly Norfolk Green) is a bus operator based in King's Lynn in Norfolk, England.  It operates 33 public bus services in the counties of Norfolk, Cambridgeshire and Lincolnshire as well as numerous school and college services.  It is a subsidiary of Stagecoach.

South Lancashire Tramways: South Lancashire Tramways was a system of electric tramways in south Lancashire authorised by the South Lancashire Tramways Act of 1900.  The "South Lancashire Tramways Company" was authorised by the act to build over 62 mi of track to serve the towns between St Helens (now in Merseyside), Swinton, Westhoughton and Hulton Lane where the Bolton Corporation system ended.  The system was the largest standard-gauge electric tramway outside London.

Stagecoach North West: Stagecoach North West was a major operator of bus services in North West England.  It was a subsidiary of the Stagecoach Group, and had its origins in the purchase of Cumberland in 1987 and Ribble Motor Services in 1988 from the National Bus Company.  The head office of Stagecoach North West was in Carlisle.  Although the cities of Liverpool and Manchester are in the North West of England, Stagecoach Manchester and Stagecoach Merseyside were run as separate divisions.

Ribble Motor Services: Ribble Motor Services was a large regional bus operator in the North West England based in Preston.

Stagecoach Merseyside &amp; South Lancashire: Stagecoach Merseyside & South Lancashire (Glenvale Transport Limited [In Liverpool]) is a major operator of bus services in North West England.  It is a subsidiary of the Stagecoach Group, and has its origins in the purchase of Ribble in 1988 from the National Bus Company and Glenvale Transport in 2005.  The head office of Stagecoach Merseyside & South Lancashire is in Liverpool and was formed in 2011 following the merger of Stagecoach Merseyside and Ribble Motor Services which was the Chorley and Preston operations of Stagecoach North West.

Lancashire United Transport: Lancashire United Transport (LUT) was a tram, bus and trolleybus operator based at Howe Bridge in Atherton, 10 miles north west of Manchester.  It had the distinction of being the largest independent bus operator in the UK until its acquisition by Greater Manchester PTE in 1976.

Stagecoach Cumbria &amp; North Lancashire: Stagecoach Cumbria & North Lancashire is a major operator of bus services in North West England.  It is a subsidiary of the Stagecoach Group, and has its origins in the purchase of Cumberland in 1987 and Ribble in 1988 from the National Bus Company.  The head office of Stagecoach Cumbria & North Lancashire is in Carlisle.  It was previously known as Stagecoach North West until 1 September, when Stagecoach Merseyside joined Preston and Chorley depots to form Stagecoach Merseyside & South Lancashire.

Stagecoach Merseyside: Stagecoach Merseyside is a major operator of bus services in the British city of Liverpool and in the surrounding area of Merseyside.  It is a subsidiary of the Stagecoach Group.  It was formed in July 2005 due to the acquisition of Glenvale Transport (GT), which in turn had initially been formed by ex-MTL managers bidding for company, following a Competition Commission ruling that Arriva must sell their newly acquired Gillmoss depot to preserve the competition within the Merseyside area.

Stagecoach Sheffield: Stagecoach Sheffield is a bus operator based in Sheffield, England, a subsidiary of the Stagecoach Group.  It was formed from the Sheffield-based operations of the Yorkshire Traction Group, purchased by Stagecoach in 2005.  Most bus services in Sheffield are operated by Stagecoach Sheffield or First South Yorkshire.

Supporting paragraphs: Stagecoach Merseyside &amp; South Lancashire Ribble Motor Services
Answer: Preston