Used to love playing count the different seat covers. Back then, bus seats were the same basica design, so if there was a cusion or seat back readly available, then it got used regardless of pattern.

As for vehicle types, here is a basic list (not including demos or going into mechanical specification) used by the big 3 (or predecessors).... There is probably a few more than this going further back, or certain oddball vehicles and secondhand vehicles briefly operated. But these are the main examples I can think of.

ADL Enviro 200 Dart
Arriva - https://www.flickr.com/photos/gjm-photog...4059141328
Go - https://www.flickr.com/photos/gjm-photog...1288418644
Stagecoach - https://www.flickr.com/photos/gjm-photog...1603149321

ADL Enviro 400
Arriva - https://www.flickr.com/photos/gjm-photog...2985896640
Go - https://www.flickr.com/photos/gjm-photog...2524680402
Stagecoach - https://www.flickr.com/photos/gjm-photog...9645314048

ADL Enviro 400MMC
Arriva - https://www.flickr.com/photos/gjm-photog...7040087486
Go - https://www.flickr.com/photos/gjm-photog...2037701102
Stagecoach - https://www.flickr.com/photos/gjm-photog...5841412448

Bristol LH - ECW
Arriva - https://www.flickr.com/photos/131962719@N04/52336288309 (Photo by Ken Weaver)
Go - https://www.flickr.com/photos/66289212@N07/51150547603 (Photo by Graeme Phillips)
Stagecoach - https://www.flickr.com/photos/jncarter1962/51865317812 (Photo by John Carter)

Bristol RE - ECW
Arriva - https://www.flickr.com/photos/gjm-photog...6346395957
Go - https://www.flickr.com/photos/theorigina...9712038823 (Photo by Zippy)
Stagecoach - https://www.flickr.com/photos/gjm-photog...9797788858

Bristol VR (Series 2) - ECW
Arriva - https://www.flickr.com/photos/jncarter1962/14713250377 (Photo by John Carter)
Go - https://www.flickr.com/photos/jncarter1962/24694022228 (Photo by John Carter)
Stagecoach - https://www.flickr.com/photos/johnmightycat/52098153851 (Photo by John Law)

Dennis Dart - Plaxton Pointer
Arriva - https://www.flickr.com/photos/gjm-photog...0580667297
Go - https://www.flickr.com/photos/gjm-photog...5849491792
Stagecoach - https://www.flickr.com/photos/gjm-photog...9620240252

Dennis (ADL / Transbus) Dart SLF - Plaxton (ADL / Transbus) Pointer 2
Arriva - https://www.flickr.com/photos/gjm-photog...8426995202
Go - https://www.flickr.com/photos/gjm-photog...0059740558
Stagecoach - https://www.flickr.com/photos/gjm-photog...3951994446

Leyland Atlantean - Alexander AL
Arriva - https://www.flickr.com/photos/nedbasher/5700085480 (Photo by Ned Basher)
Go - https://www.flickr.com/photos/nedbasher/5641916666 (Photo by Ned Basher)
Stagecoach - https://www.flickr.com/photos/gjm-photog...2075263682

Leyland Leopard - Alexander Y Type
Arriva - https://www.flickr.com/photos/jncarter1962/16225762357 (Photo by John Carter)
Go - https://www.flickr.com/photos/77000628@N02/50969413481 (Photo by David Devoy)
Stagecoach - https://www.flickr.com/photos/131962719@N04/18172860091 (Photo by Ken Weaver) - Thought these looked fantastic in TWPTE livery.

Leyland Leopard - ECW B51
Arriva - https://www.flickr.com/photos/45726467@N02/14371394993 (Photo by David Beardmore) - This was the last Leyland Leopard built.
Go - https://www.flickr.com/photos/jncarter1962/6985835529 (Photo by John Carter)
Stagecoach - https://www.flickr.com/photos/ermintrude73/21437085522/ (photo by Ermintrude73)

Leyland Lynx Mk1
Arriva - https://www.flickr.com/photos/183419366@N07/49885687853 (By Ed's Bus Photos) - These were rebuilt with Mk2 front parts.
Go - https://www.flickr.com/photos/ian_simpson/2938247368 (Photo by Ian Simpson)
Stagecoach - https://www.flickr.com/photos/gjm-photog...6736019006

Leyland Lynx Mk2
Arriva - https://www.flickr.com/photos/gjm-photog...9710740792
Go - https://www.flickr.com/photos/gjm-photog...0429821981
Stagecoach - https://www.flickr.com/photos/gjm-photog...9864456053

Leyland National Mk1
Arriva - https://www.flickr.com/photos/54358344@N05/43543990244 (Photo by Bob J B)
Go - https://www.flickr.com/photos/jncarter1962/39544680562 (Photo by John Carter)
Stagecoach - https://www.flickr.com/photos/23207961@N07/3519134076 (Photo by Brian)

Leyland National Mk2
Arriva - https://www.flickr.com/photos/nedbasher/6522558579 (Photo by Ned Basher)
Go - https://www.flickr.com/photos/gjm-photog...6098371936
Stagecoach - https://www.flickr.com/photos/solenteer/4952176318 (Photo by Solenteer)

Leyland Olympian - Alexander RH
Arriva - https://www.flickr.com/photos/gjm-photog...8788373237
Go - https://www.flickr.com/photos/gjm-photog...8959732851
Stagecoach - https://www.flickr.com/photos/gjm-photog...5828409544

Leyland Olympian - ECW (Bus Body)
Arriva - https://www.flickr.com/photos/gjm-photog...5747212804
Go - https://www.flickr.com/photos/gjm-photog...6626588392
Stagecoach - https://www.flickr.com/photos/gjm-photog...6367078181

Leyland Olympian - N-C Palatine 1
Arriva - https://www.flickr.com/photos/gjm-photog...1831278565
Go - https://www.flickr.com/photos/gjm-photog...4853479026
Stagecoach - https://www.flickr.com/photos/gjm-photog...9868638396

Leyland Tiger - Plaxton
Arriva - https://www.flickr.com/photos/gjm-photog...3746692415
Go - https://www.flickr.com/photos/gjm-photog...8839796213
Stagecoach - https://www.flickr.com/photos/jncarter1962/23245218953 (Photo by John Carter)

MCW Metrobus Mk1
Arriva - https://www.flickr.com/photos/gjm-photog...9144069221
Go - https://www.flickr.com/photos/knoxrj/52474828383 (Photo by Knox Family)
Stagecoach - https://www.flickr.com/photos/busfreakbrian/10900269375 (Photo by Brian H)

MCW Metrorider
Arriva - https://www.flickr.com/photos/nedbasher/7030160185 (Photo by Ned Basher)
Go - https://www.flickr.com/photos/jncarter1962/6378976091 (Photo by John Carter)
Stagecoach - https://www.flickr.com/photos/jncarter1962/8400205708 (Photo by John Carter)

Optare Alero
Arriva - https://www.flickr.com/photos/gjm-photog...0577564092
Go - https://www.flickr.com/photos/gjm-photog...3882335732
Stagecoach - https://www.flickr.com/photos/gjm-photog...8100848131

Optare MetroRider (Series 2)
Arriva - https://www.flickr.com/photos/gjm-photog...1883354422
Go - https://www.flickr.com/photos/gjm-photog...6825422866
Stagecoach - https://www.flickr.com/photos/57727182@N08/27424551722 (Photo by George)

Optare Solo
Arriva - https://www.flickr.com/photos/gjm-photog...1504635958
Go - https://www.flickr.com/photos/gjm-photog...9118220573
Stagecoach - https://www.flickr.com/photos/gjm-photog...6867244270

Volvo B6 - Plaxton Pointer
Arriva - https://www.flickr.com/photos/gjm-photog...9976413933
Go - https://www.flickr.com/photos/gjm-photog...6285800682
Stagecoach - https://www.flickr.com/photos/gjm-photog...8382935151

Volvo B10B - Alexander Strider
Arriva - https://www.flickr.com/photos/gjm-photog...9473257638
Go - https://www.flickr.com/photos/gjm-photog...9692776197
Stagecoach - https://www.flickr.com/photos/gjm-photog...7391919764

Volvo B10BLE - Alexander ALX300
Arriva - https://www.flickr.com/photos/gjm-photog...4157933780
Go - https://www.flickr.com/photos/gjm-photog...0813203993
Stagecoach - https://www.flickr.com/photos/gjm-photog...1897688124

Volvo Olympian - N-C Palatine 1
Arriva - https://www.flickr.com/photos/gjm-photog...0828337466
Go - https://www.flickr.com/photos/gjm-photog...0043250338
Stagecoach - https://www.flickr.com/photos/gjm-photog...8467233192