What you have to remember is that these guys aint American.
You travel to any place of high academia here, like Oxford or Cambridge (and more countrified areas), and you will see people dressing like Smith all over the place.
And hell, you cant walk through central London without seeing people dressed like Tennant.

The mod culture never really went away here, there has always been a huge following. If you go into Carnaby Street, as a good example, and despite it now being a very trendy street, its still got a huge mod shop there, and is still a place thats fully associated with mod shit.

I'd say if a person wearing a mod suit appeared in 1890, he wouldnt look that different to if a modern businessman appeared there.
It would just look like another form of formal dress.

Now if you turn up wearing a denim jacket or jogging bottoms, now that would look outlandish to them!