Computer Killers (1973) on Netflix

A young singer from a very seventies band decides he needs a vacation, so he travels to a creepy mansion in the heart of rural England to have all his inhibitions removed. He meets up with a sweet innocent girl who is travelling there to meet her aunt, who turns out to be a nasty matron type person. Eventually, they arrive to discover nearly all the other hospital inhabitants to be under some kind of mind control, with big scars on their heads. Not being in the slightest bit disturbed by this, they proceed to have lots of sex. Other guests, meanwhile realise something is amiss, and try to escape only to be decapitated by some kind of killer car, or to be beaten to death by mad motorcyclists. Eventually realising something is up, our hero and heroine have a big fight scene with the bikers, two at a time, and escape in the villains car.