Another one remembered:
" 'The Book Tower'e was always very entertaining, I especially liked the teapot which would always contain something unexpected, like piglets, or sand... then there was that mysterious room out back, which Tom would look at through a hole in the book tower painting. The room was always full of school children dressed up as something relevant to an activity book... Children's TV from Yorkshire."
And a different one said:
"The Book Tower : Tom Baker brings out books from his Teapot of Plenty." [It must have been a TARDIS.]
And finally, one stated:
"... Also had Leeds Bridge House in the opening title sequence,depicting the 'Book Tower' that Tom Baker was supposedly in."
Here is a photo of that building:
But I can't see that it was the structure used in the opening credits. Unless "The Book Tower," clip was from a different angle/side of the building, than the one shown in the above photo..