I do not know how much development has gone on with PakBritain recently (I found the original download and discussion from the forum archive here (http://archive.forum.simutrans.com/topic/04105.0/index.html)), but I thought that it might be worthwhile re-configuring its speedbonus.tab to match the speeds of the vehicles in that set. A copy is attached. Do reply to this thread with any comments/questions.
Incidentally, the beta version of PakBritain that I have is most impressive so far - I should very much like to see any further development. I might even be able to provide some assistance if I have time (I can't draw for toffee, though, so I won't be able to create any artwork).
Edit: Updated the file to re-adjust the rail speed bonuses for the mid-20th century onwards, which were set too high in the original file.
Edit 2: Updated the file to take account of the fact that the speedbonus is interpolated by the program, and also to make the bonus more generous for aircraft.
Edit 3: The speed bonus that I updated last time contained an error which would cause the program to crash on startup. A corrected version is attached.
I have now updated this file to take account of the feedback and discussion here (http://forum.simutrans.com/index.php?topic=996.0).
Update: I have now corrected an error in the latest version which would cause a crash on startup.