I am a big fan of Hammer Horror. Over the years they produced some amazing films that are among some of the best in the horror genre. I must admit, however, I couldn't get too excited about Paranoiac. Yes, it stars THE Oliver Reed [Oliver, Gladiator] as Simon Ashby a wealthy socialite with a destructive personality who lives with a crazy family. Yes, he gives a very good performance. But Paranoiac left me feeling like I'd seen it a hundred times before. For me there were no surprises. The "twists" in the plot I saw coming a mile away.
This is not to suggest that Paranoiac is not a good film. It is well made and reasonably well acted all around. It's just...well...I can't put my finger on it but I found the whole thing a bit boring. For whatever reason, it just didn't work for me. But maybe it will work for you.
The critics seem somewhat fond of it. However, it felt more like a melodrama to me than a horror film. Do with it what you will.
For more info check out the film's entry in IMDB.