With their crowns slipping, strident style queens Trinny Woodall and Susannah Constantine still have one has-been to make over - their career. The pair haven't chosen an obvious route for revival, sending themselves up in a warts-and-all mockumentary (originally shown in instalments online). Cameras follow them as they attempt to re-establish their TV profile. Some of it is hilarious. A drunk Constantine chain smokes her way through couples therapy with Woodall, and the desperate duo flog their range of underwear at a golf trade fair.

Earlier this summer, fashionistas Trinny Woodall and Susannah Constantine posted a series of spoof films on the internet about their supposed attempts to get back on TV. A mixture of improvised and scripted scenes, spattered with F-words, they've been edited into a one-off comedy. It's supposedly modelled on Curb Your Enthusiasm, but at times the screaming and swearing make it more like something a group of drunken and/or stoned students would produce. That said, you have to admire them for mercilessly poking fun at themselves. "We used to be huge," screams Trinny in-between colonics, while Susannah spends most of her time in a cigarette- and alcohol-fuelled haze. It's fun to star-spot too: Lulu, David Furnish, Neil Fox and even a bemused Duke of Wessex make an appearance.

There's actually more bum than boom on display in this very revealing fly-on-the-wall documentary. If it's not Susannah Constantine modelling flesh-coloured control knickers at a trade show, it's Trinny Woodall flashing her thong at the camera or having her bum cheeks slapped during one of her regular massage sessions.

The girls have promised this film will show viewers what they're really like and what we learn straight off is that they've got a better sense of humour than you might have given them credit for - because none of this is real. A few die-hard fans of the bap-grabbing fashionistas might have already seen this mockumentary when it was aired online in bite-size instalments.

Here, Channel 4 have cannily repackaged it into an hour-long show and it works surprisingly well. It plays on their desperate attempts to get back on to our TV screens any which way they can after getting dumped by their agent and losing a lucrative contract with Cillit Bang cleaning products.

"Your problem is you're too honest," one talent agent tells them. "You want to look at that Chinese woman. The big tall one with the bins on. He'll tell someone who's an absolute munter they look the bollocks." As well as some Gok Wan rivalry, there's an attempted makeover on some jockeys and lots of their celebrity chums playing themselves - including Lulu, Vanessa Feltz and David Furnish - plus a surprising cameo from Prince Edward.

Putting the boob-grabbing former queens of TV on Curb-style mockumentary seems as godawful an idea as Monkey Tennis or Robson Green's Extreme Fishing (which actually happened).

Yet this bizarre, sometimes hilarious show works unexpectedly well, with the pair squabbling and squawking, bemoaning Gok Wan's popularity and plumbing the depths of celebrity endorsement.

Once the high priestesses of makeover TV and initially watchable despite their 'tell-it-like-it-is' rudeness, we find Trinny Woodall and Susannah Constantine attempting to recapture former glories in From Boom to Bust (see what they did there with the title?)

In Thursday's opener, the fashionistas gunned for a return to the limelight in the shape of a Cillit Bang ad only for their decline on the celebrity stock market to torpedo the deal and lose the duo their longstanding agent.

Rent-a-celebs such as Lulu and Dr Fox popped up as talking heads and familiar comedians including Katy Wix (Not Going Out) and Nicholas Burns (Nathan Barley) portrayed Trinny and Susannah's long-suffering staff.

At an hour, it was a little too long to sustain the joke but with teetotal Trin and Chardonnay-quaffing Suze impressively game for self-parody, it might be the vehicle they need to knock Gok off the makeover perch.

Trinny and Susannah return from TV wilderness

They appeared destined for the television wasteland after being unceremoniously dumped by ITV two years ago. However, Trinny Woodall, 46, and Susannah Constantine, 48 have made an astonishing comeback - with the pair returning to terrestrial television later this month.

Very slightly disappointing guests this week, although Lee Mack's team does manage to accommodate the widely differing talents of beaming West End musical star Michael Ball and sulphurous TV grump Charlie Brooker. Both are good value (Ball even makes a sly joke about drugs), but on David Mitchell's team Trinny Woodall and Reece Shearsmith seem, well, out of sorts. No matter. This show has no problem overcoming the handicap of less-than-sparkling guests to deliver a half-hour of laughs. Tonight the flights of fancy (or are they brute facts?) include Shearsmith's alleged spell working in a themed funeral parlour and Brooker's claim that he pretended to a girlfriend for six years that he was partially deaf. But crucially, do three members of the cabinet subscribe to David Mitchell's Twitter feed? And, if so, who are they? You'll have to watch to find out.