Headcases, ITV1<br/>The Wall, BBC3<br/>Frankie Howerd: Rather You Than Me, BBC4<br/>The Strange Luck of VS Naipaul, BBC4

Sometimes, TV is simply not worth the cable space: It's been a week of small-screen turmoil, and, to top it all, the BBC iPlayer is such a hit that the net's groaning under the strain

Television, like the stock market, is unstable at the moment. Last week, a profile of Frankie Howerd failed to raise a single laugh; a profile of VS Naipaul, on the other hand, revealed comical levels of writerly self-absorption. "It's not in my power to damage," he sighed; next, he called a young journalist a "turd". More of this dismaying pantomime later.

Fluctuations, first, should be registered regarding what you can or can't say on TV. Things are changing fast. It started with BBC2's White Season, which self-consciously broke taboos by incorporating anti-immigration views into the scheduling; now, however, last week's controversy has become this week's orthodoxy. Channel 4 followed suit with a much more straightforward documentary, Immigration: The Inconvenient Truth, in which Rageh Omaar listened carefully and sympathetically to expressions of alienation and disenfranchisement, and talk of an immigration "crisis", much of it from people who were themselves second-generation immigrants. Finally, to top off a week of TV turmoil, the BBC iPlayer gawn broke the internets!

Sorry, "the internets" is just my favourite George Bushism. The fact is that the BBC iPlayer has been an instant hit, which means internet cables are groaning and so are service providers. Clearly, everyone's busy downloading Wainwright Walks and BBC4 documentaries about Bach. It's not as if our cables are jammed with the pixels of titillating, offensively vacuous BBC trash such as Dawn Goes Lesbian ... is it? Oh dear, don't look at the list of the top 10 downloaded programmes. Why is the truth always so inconvenient?

There was a lot of telly that wasn't worth the cable space, last week, so let's write it off quickly. Headcases is a satire on ITV with a new aesthetic (grotesque CGI characters that move in creaky, mesmerising slo-mo, like a bullet underwater) and an old ambition (Spitting Image-style, it would like its jokes to dominate careers). It was a poor start, all attitude and no punchlines, but over a decade of Spitting Image yielded about three jokes worth remembering, so let's give it a little longer to find its feet.

The Wall (BBC3) is a shiny, shouty, corner-cutting studio show. Producers didn't bother with scripts or jokes, depending instead upon the laziest sub-Boosh surrealism ("Hey, let's have a talking... wall?"). All it had to declare was its star guests (We Are Klang, Jonathan Ross) and its "hot property" presenter Alexa Chung – good job everyone's forgotten about Get a Grip, the woeful TV double act she and Ben Elton perpetrated last year. Well, almost everyone.... Here, she gets a second chance. For all her cool, she turns out to be charmingly reminiscent of a friendly prefect at an expensive school – forever balancing her innately posh, clever confidence against a cringing display of self-deprecation. What is her talent, exactly? It's hard to say, but like all the best prefects, she inspires people to want to be her, which is, I suppose, a kind of talent. Anyway, while you'd never call The Wall good, it's certainly better than Lily Allen and Friends.

The crying clown is not just a cliché but an eternal truth, so BBC4's Curse of Comedy season has been a bit of a blessing, especially for Equity members in search of a troubled comedy icon to impersonate. David Walliams had the final bite of the cherry with Frankie Howerd: Rather You Than Me. He gave a perverse, sad performance, and one that, I would hazard, had been fatally over-thought. Walliams seemed to be deliberately deadening all his comic flair, crushing Peter Harness's witty script flat. He even sat on "Tennis, Dennis?" How could he?

Of all people, only he could: as a top comedian he had something else to prove. Despite the considerable pathos, and the lovely detail (the toupée on the teapot; the gags about Gilbert Harding) you were left feeling robbed, and wondering what that lovely waiter saw in Frankie Howerd. Also wondering why the waiter bought him a present of a tatty vintage Monopoly set, not a new one? The curse of the BBC4 budget, my dears.

The sensitive poetic sensibility of the classic Arena documentary has not been corrupted. They are still padding out portraits of highly controversial authors with shots of bobbing leaves and recumbent sheep. It's a civilised way to run a documentary, and one which still allows for a subject to be furnished, over a long, leisurely unspooling process, with enough rope to hang himself. So it was with The Strange Luck of VS Naipaul. Passages from his work were given breathing room, read beautifully by Diana Athill. Digressions and ruminations and other such irrelevancies were included, and became essential.

Cumulatively, a portrait built up of a compulsively truthful man, but also a cruel one. He let so many little details slip. Here, a letter left unanswered. There, a mistress of 25 years that he simply didn't see again. A proposal he made – "Would you consider one day becoming Lady Naipaul?" – when his existing wife was not quite dead from cancer. And this was the authorised version. By the end, he had attained in my eyes (and I say this as a great admirer of his work) a vampiric aspect – draining women, without gratitude.

"The rest is a kind of scaffolding," he explained airily, "that props up the writing being."