In 1957, Hammer Studios shot part of 'Quatermass 2' in the town, cannily linking Hemel Hempstead's construction to the fictional 'Winnerden Flats' being built to house workers at the 'artificial food plant' in the story. Basically a big building site, the town proved an apt and eerie location, starting with the approach on a big empty road which abruptly terminates in the middle of nowhere.
Finding a dirt track that leads to the beginnings of a huge estate, Quatermass stops to interact with a few of the locals. The lady with a speaking role is an actress, but the ladies in the background are real residents, lucky enough to have been allocated one of the few completed houses on a project that still has years to run. There isn't even a pavement for them to push their shopping baskets along.
I believe this is the area of Hemel Hempstead known as Warner's End, although I stand to be corrected. Like all the individual estates in the new town it was designed to have its own mini civic centre: a parade of shops, a pub, a Doctor's surgery, some public art. In the film, however, all they have to look forward to is Whist on Wednesdays (cash prizes), and all there is to see are the abandoned double decker buses that brought them to this brave new world.
Incidentally, I have been to Hemel Hempstead and it's quite nice, really, with very little evidence of alien invasion.