yes, it really was some powerful TV, certainly stayed with me for over 30yrs !
made electric pylons seem spooky, in a similar way to Hitchcock's Birds made you look twice at every crow !
there's a fantastic pictorial of the whole 10 episodes here, with screengrabs from UKGold, as I don't think I'll ever be watching it again - http://www.thechestnut.com/changes-1.htm
one surprising thing is, although I'm pretty sure I saw the whole series, I don't specifically remember the Indian family at all - I would have thought it would have been unusual back in the '70's for their roles to be so central. (Maybe not ?) Certainly where I lived there were no Seikh's.
I do remember losing interest part way through the series, and that the ending was a bit poor (without recalling the rock at all !)
And as someone mentioned on one of the sites, this show might have been better scheduled following Tomorrow's World or TOTP, rather than being followed by Paddington Bear !