The series was beautifully cast and well-crafted, but comparisons to the Forsyte Saga are a bit unfair because anything will inevitably be found wanting. Only I Claudius has been as successful.
Huxley was a fascinating, visionary writer whose entire body of work still bears reading, but he was hardly a master stylist and lacked the deft skill of a Waugh at either satire or characterization. He is probably best compared to Orwell, whose work he influenced, and PCP has the feel of Orwell's lesser works like Keep the Apidistra Flying. In PCP Huxley was concerned with the rise of British Fascism and the series contains characters based on Oswald Mosley and the painter Augustus John, among others. Note: the novel itself, published in 1928, presciently preceded Mosley, but the TV production uses the more famous man as its model (and why not?)
Unlike the novel, the most dynamic character in the TV version is that of the rather dull protagonist's father, who is portrayed as a pop-faced aging Mayfair dandy and whose line "A bay-buh? Shorely not a bay-buh!" when told that his very young secretary is pregnant by him, achieved a brief popular mimicry.
The series was adapted for TV, incidentally, by Simon Raven, whose spy novels and gossipy hatchet-jobs on the famous of his day are still enjoyable if slight reading.
It's a shame this hasn't been released by the BBC (though if the Beeb were capable of shame over its treatment of valuable properties from the '60s, it would have died long ago); other similar series that viewers might find of interest would be The Glittering Prizes and the earlier 80s' version of Love in a Cold Climate-- aside, of course, from Brideshead Revisited.