The left-path convert of Great Colquart was released in September 2015 and as such uses objects, splines and buses available in 2015... it
will not work out of the box and finding all the bits will be difficult.
The file listing on Aussiex is
archived on archive.org, and at the bottom of the listing there is a
GDrive mirror which still works (at time of writing). If the mirror download stops working, someone will have to contend with whatever the "action" is that will taken if you are caught and reported...
STRICTLY NO UPLOADING TO OTHER SITES. ANYONE CAUGHT DOING SO WILL BE REPORTED AND ACTION WILL BE TAKEN.
There is conveniently a list of all of the objects and splines (as generated by Map Tools) included in the Documents folder, which I have attached. I note it includes objects from Birmingham Sutton Coldfield, Bowdenham V4 and Canterbury Donors, among others.
You'll want to change the AI list and supply a new HOF file to work with more current buses I should imagine... the file listing and read-me disagree on what vehicles are actually required and some may be difficult to source.
Oh, and because it's from 2015 it has the left-path bus stop bug, so you'll want to fix that if you want passengers and AI buses to agree on where the bus stop is.