The prudish will be tested by new Brit sex therapy drama Between The Sheets (TV One, 9.35pm). The lover of edgy, challenging drama will not be so lucky.

For all the raunch, the awfully frank detail in the therapy sessions, not to mention the hot, geriatric sex talk, Between the Sheets is still a drama set firmly in the middle of the road.

This seems to be a speciality of its writer, Kay Mellor, who also penned Fat Friends, about a Yorkshire slimmers club and Band of Gold, about a group of Bradford prostitutes. Her dramas often mine risque and gritty material, and usually feature a gifted cast, but somehow remain as downhome and cosy as the local chippy.

Between the Sheets follows several storylines, none of them particularly original. Peter (Alun Armstrong), a successful real estate developer and lapdancing club owner, and wife Hazel (Brenda Blethyn) find their middle-aged marriage has lapsed into misery and mutual misunderstanding.

Last week's first episode of the ITV drama opened with a wedding, and with all the kids off her hands, Hazel is ready to cut loose from her domestic unhappiness. She's done a bunk and is demanding Peter attend sex counselling with her.

Peter, whose ownership of a Tony Soprano Bada-bing-style club seems just an excuse to lace the show with lots of naked female flesh, isn't having a bar of any suggestion that he has sexual problems.

Hazel, a good Catholic woman, is a bundle of repression just waiting to be let go. Release is at hand in the form of sex counsellor Alona, who sets her some naughty floral homework straight from Lady Chatterley's Lover.

True to the cliche, Alona is not enjoying the best sex-life herself. Her probation officer partner isn't performing in the sack and she suspects he's not telling her all the details about the young female client who's started stalking him.

ITV called Between the Sheets a "no-holds barred drama about a female sex therapist and the couples she is counselling".

It actually appears to be more a middle-aged version of the chick drama, a point emphasised by its screening last week after the final of Irish gal pal show Any Time Now. Presumably the older set stay up later.

The later slot might also be explained by what the pensioners get up to. Someone's been watching too much Sex and the City, and it isn't the young folk.

Liz Smith and Norman Wisdom play Peter's randy mother Nana Audrey and her lover, the lawn-mower man Maurice. Nana's graphic depictions of her sex life to a squirming Hazel put Carrie, Samantha and co in the shade. The geriatrics are the only couple enjoying a fully functional sexual relationship on the show - an example of the drama's heavyhanded attempts at comedy.

The plots are pretty silly, the old folks are artificially naughty, but Between the Sheets is saved by fine performances from Armstrong and Blethyn. Blethyn in particular, her face one long contortion of misery and repression, turns all that airing of dirty laundry into something watchable and engaging.