Final episode of the immensely enjoyable sitcom written by and starring Sue Perkins as a gay vet. The day has finally come for Sara (Perkins) to come out to her parents, but first an almost French farce-style mousetrap must be set to ensure that it's even more difficult, embarrassing and disaster-strewn than she could have possibly imagined. What this last episode lacks in believable plotting it more than makes up for in gags and snakebite antidotes. Roll on series two.

Despite the likeability of Sue Perkins's geeky-gawky vet Sara, this sitcom has relied on hackneyed set-ups and caricatures. In tonight's finale, it's D-Day, when Sara vows to tell her parents she's gay. Joanna Scanlan chomps through what remains of the scenery as Sara's New Age therapist.

Hardly anyone likes Heading Out, it's been kicked to death then dumped in a shallow grave by audiences and critics, so it's perverse to make it recommended viewing. Except I like it. I know it's as annoying and stupid as everyone says it is. But it's harmless and it doesn't try to be novel or pioneering, and I've laughed at least once at each episode. But never mind, it ends tonight as hapless vet Sara at last decides she absolutely MUST come out to her parents. Cue a disastrous dinner party.

It's not a revolutionary sitcom, but that may well be the clandestine unique selling point of Heading Out: it places a gay character unremarkably at the centre of things, and lets her get on with it. Tonight, Sara (Sue Perkins) builds up to coming out to her own parents, by first telling someone else's: in this case, the Wodehousian eccentrics who gave issue to Toria, her life coach (the ace Joanna Scanlan). Best friends Jamie and Justine are, of course, on board for the reasonably amusing ride.

Excitable vet Sara and her daft friends spend a hellish night in the chilly ancestral home of her barking-mad life coach Toria. It turns out Toria's hearty parents are as bonkers as she is, which is just as well as Toria wants Sara (Sue Perkins) to practise on them how she will come out as a lesbian to her own mum and dad. Toria's family (motto "Kill Them All"), including Dawn French in a grey wig as Toria's mum, is impertinently intrusive and the night is full of farcical misunderstandings as well as ghostly noises on the landing.

Determined to prepare Sara (Sue Perkins) for the impending visit from her parents, Toria (Joanna Scanlan) takes her, Justine (Nicola Walker) and Jamie (Dominic Coleman) to her own parents' stately home in the country to give her a "coming-out trial run". A cosy half-hour of affable nonsense, kept afloat by Perkins's ability to be simultaneously droll and vulnerable.

Steve Pemberton guests as a bizarre, equine-obsessed vet inspector who turns up at Sara's very peculiar practice. The place is even more shambolic after Daniel deserts his post to play sex games in his suburban front room. So Sara's simple-minded friend Justine (Nicola Walker) steps in to staff the reception desk, adopting a northern accent because she's a fan of All Creatures Great and Small.

It's a cheerful half-hour of amiable nonsense led by Sue Perkins. I know it hasn't set the world on fire, but its heart is in the right place and the gags are often clever.

It's a cameo-crammed episode of Sue Perkins's vet-based comedy tonight. She's joined by long-time collaborator Mel Giedroyc, on top form as a brusque Russian. Then Steve Pemberton pops up as a veterinary inspector with a penchant for horses. Despite feeling curiously detached from any sort of reality, Perkins's script is sprightly and her presence is somehow reassuring - awkward but always amiable.

The jury is still out on Heading Out

I must admit that while there are moments which are both humorous and surreal, I feel let down that Sara the vet isn't a bit more Sue-like.

Heading Out was nosing toward disaster, but could have pulled back from the brink until the arrival this week of protagonist Sara's French ex-girlfriend. Some of her exes are walking cliches, and some are exercises in surrealism, and the unlucky ones are both, but at least the only one some schmuck has to bring alive is the French one, who is angry for no reason, stays for no reason and shouts for no reason, unless "we want to remake 'Allo 'Allo with lesbians" is the underlying reason, in which case, I will grudgingly remove my hat.

The jokes are stale, the punchlines are awkwardly delivered, as if the actors are deservedly ashamed, the tropes are two decades old (a therapist with made-up qualifications and a drum? Why stop there? Where's the critical mother who wants to be a grandmother, what about a nice lady vicar who likes a drink, we could use a spoilt Sloane Ranger here, if anyone's got a moment, SOMEONE CALL FRENCH AND SAUNDERS. Ask them if they've got any ideas left over from 1987).