So not 300 then
Of course people travel all the way although by observation most of TPE custom is shorter runs. I have traveled form Manchester to Glasgow often enough as it is cheaper than Virgin. The train is fine for that journey. It just isn't long enough.
The same train is perfectly fine in the same configuration for Crewe - Euston which takes 2hrs 55mins compared to Manchester - Glasgow which takes 3hrs 13 mins despite the first being a shorter journey by about 100 miles.
Of the problems with TPE, on any objective viewing, train type can not be said to be one of them.