This was a teatime serial for older children, based on a book called 'Marianne Dreams'.
Marianne was a girl who had broken her leg and had to stay in bed - she found a special pencil and drew a mysterious house, which she then visited in her dreams (nightmares, rather).
There was also a disabled boy who was trapped in the house and they could not leave because big rocks with eyes were encroaching all the time, whispering and chanting 'we're coming, we're coming!'
It was one of the most frightening things I had ever seen. I'm happy to say that I found a dvd of it on the internet, so we watched it again recently. It's still scary, but my kids laughed their socks off! In these days of computer-generated special effects, it was a big disappointment to them. How unsophisticated we were in the '70's!