Where can I find Creep, with Franka Potente?

I remember watching this horror movie years ago and really enjoying it. It's about a woman trapped on the London Underground and trying to get out. And there's.... a creature.

There is a homeless man and his girlfriend, (who eventually died) and a sewerage worker being trained (who, as I recall, also gets it).

The monster later turns out to be some sort of foetal experiment who was trying the same with others....?

I saw this film many years ago and it seems to be shamefully underrated. I have never really heard of read anybody talking about it since.

Does anyone know where I can watch this (preferably for free) in the UK?