A brief mention from the London Bus Fleet Audit report:
As of 31st March 2019, there are 6,547 double decker buses and 2595 single decker buses. The number of types in the report are: 10 AEC Routemasters, 1,000 Hybrid New Routemasters, 5,298 diesel buses, 155 zero emission electric buses, 10 hydrogen fuel cell buses and 2669 hybrid buses, they make a total of 9,142 buses for London.
You can read the full report of the London bus fleet audit which mentioned the number of bus types and Euro emission standards used for London Bus services in the PDF below:
http://content.tfl.gov.uk/fleet-audit-report-31-march-2019.pdf
London Buses Fleet List
The operational vehicle data is the fleet list of buses used for London bus tendered services. The fleet list shows the registration (number plate), fleet number, operator, registration date, age of vehicle, bus type, chassis and body type, type of engine, Euro emissions and more.
Link to the PDF:
https://tfl.gov.uk/cdn/static/cms/documents/fleet-list-annual-audit-report-31-march-2019.pdf
You can obtain more fleet lists of buses in Britain and elsewhere on the UK Buses website.
http://www.ukbuses.co.uk
Other websites containing fleet lists:
Bus Lists On The Web
http://www.buslistsontheweb.co.uk
Bus Γireann
https://www.buseireann.ie/inner.php?id=396
Dublin Bus
https://www.dublinbus.ie/About-Us/Dublin-Bus-Fleet/
Big Red Book
TfL has also released their latest Big Red Book under a
https://www.whatdotheyknow.com/request/574146/response/1365927/attach/3/BigRed%20Book%202019.pdf
You can also download the previous edition of the Big Red Book (released under a
Link to the PDF:
https://www.whatdotheyknow.com/request/411290/response/991787/attach/3/Big%20Red%20Book%20v4.pdf
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Image attribution
By Sludge G - New CT Plus buses on the 26, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=49459692