Just as a matter of historical interest here is a list of now sadly defunct UK airlines:
AB Airlines (ceased operations 1999)
air2000 (now First Choice Airways)
Air Anglia (precursor of AirUK, now part of KLM's Cityhopper division)
Air Bristol
Air Caledonian (2003 - 05)
Air Cordial (ceased operations 2004)
Air Europe (1979 - 91)
Airfreight Express (1999 - 2003)
Air Scandic (1997 - 2005)
AirUK
Airways International Cymru (1984 - 88)
Ambassador Airways (1992 - 94)
Amber Airways
Anglo Cargo (1983 -92)
Aquila Airways
Autair International (precursor of Court Line)
AV8 Air
Bookajet (2003 - 04, to Club 328)
British Airtours (former charter subsidiary of British Airways)
British Airways Ltd (1935 - 39)
BCAL - British Caledonian Airways (1970 - 88, acquired by British Airways)
British Cargo Airlines (1979 - 80)
British Continental Airways (ceased operations 1935)
British Eagle (ceased operations in 1968)
British European Airways (BEA) (1946 - 74, to British Airways)
British European (became flybe)
British Marine Air Navigation Co (1923 - 24)
BOAC - British Overseas Airways Corporation (1939 - 74, to British Airways)
British Regional Airlines (1997 - 2002)
British South American Airways (BSSA) (1946 - 49)
British United Air Ferries
British United Airways (1960 - 70, merged with Caledonian)
British World Airlines (1946 - 2001)
Brymon Airways (1972 - 2002)
Buzz (1999 - 2003, acquired by Ryanair)
Caledonian Airways (1961 - 70 and 1974 - 2000)
Cambrian Airways (1935 - 76)
Channel Airways (ceased operations in 1972)
CityFlyer Express (1991 - 2002)
Court Line (ceased operations in 1974)
Daimler Airways (1922 - 24)
Dan-Air London (1953 - 92, to Caledonian Airways (second incarnation))
Debonair (1995 - 99)
Duo Airways (2003 - 04)
Euravia (became Britannia Airways)
Excalibur Airways (1992 - 96)
Flying Colours (1997 - 2000)
Flykeen Airways (1968 - 2005, to A2B Airways)
Gill Airways (1969 - 2001)
Go Fly (1998 - 2003, acquired by easyJet)
HC Airlines (1978 - 2002)
Highland Express Airways (1984 - 87)
Hillman's Airways (1931 - 35)
Imperial Airways (1924-1939)
Instone Airline (1921 - 24 and 1977 - 95)
Invicta International Airlines (1964 - 81)
Jersey European (became flybe)
JMC Air (renamed Thomas Cook Airlines in 2002)
KLM UK (1980 - 2003)
Laker Airways (1966 - 82)
Maersk UK (1983 - 2003)
Manx Airlines (1982 - 2002)
Northeast Airlines (1951 - 73)
Orion Airways (1978 - 89)
Prime Air (2001 - 02)
Princess Air (1989 - 91)
Red Coat Air Cargo (1977 - 82)
Sabre Airways (1994 - 2001, now Excel Airways)
Scimitar Airlines (1979 - 82)
Silver City (airline) (became British United Air Ferries 1963)
Spartan Airlines (1933 - 35)
Tradewinds Airways (1967 - 90)
United Airways (ceased operations 1935)
Virgin Sun