Mike, do you have any of those postcards with bus drivers in them?
6918, the Wolverhampton trolleybus you mentioned is fleet number 78 (Guy BTX registered UK 9978 with H33/26R body new 1931 withdrawn 1945). "Lady Wulfrun" has posted a fascinating picture of a very similar vehicle (number 79) taken in 1937.
Perhaps Bill can update us on progress with the restoration of 78. It is surely an expensive and labour intensive project, but it will be lovely to see it restored to its former glory. Made in Wolverhampton too of course.