If you want to be cheered up, and goodness knows there's a need for it just now, Phyllida Lloyd's screen adaptation of Mamma Mia!, the hit musical, could be just the thing. That is if you happen to like Abba and want a deliriously camp and determinedly upbeat happy camper type of entertainment. There's no subtlety to it whatsoever. But it swings, even when it makes nonsense of cinematic, or even dramatic, logic.

Here we have a typically wonderful Greek island on which Donna (none other than Meryl Streep) manages a slightly grotty hotel. Donna is worried sick about money and is all the more anxious when her pretty daughter Sophie (Amanda Seyfried), who is getting married to Sky (Dominic Cooper), insists on inviting three of her mum's former lovers to the wedding.

After reading her mum's diary, Sophie adds up the dates and realises that any of the trio could be her father, and badly wants to know which it is. As it turns out, Donna is by no means certain. Nor are the men, each of whom rather likes the idea of middle-aged paternity.

Cue the arrival of businessman Sam (Pierce Brosnan), adventurer Bill ( Stellan Skarsgard) and banker Harry (Colin firth). Meanwhile, Donna has invited two of her oldest friends, Rosie (Julie Walters) and Tanya (Christine Baranski), who are amazed when told of her old sexual adventures and would rather like some of their own.

Will Sophie find out who her real father is? Will Donna and the girls find romance? Let's not spoil it; suffice to say, it takes a dozen or so Abba songs and an equal number of plot turns before we find out.

Some of the cast are professional singers, some definitely not. Some are professional dancers and some not. All are professional actors and some do not have their finest moments in the film. But everyone goes to it with a steely will as if suddenly finding themselves in a summery pantomime and thoroughly enjoying letting their hair down.

It's not all over the top, though, even if there is an awful lot of exuberant screeching and shouting. But since the cast are having such a good time, we have a chance to join in the fun as well. Walters in particular is in her element, and Baranski almost more so, while Seyfried maintains a piquant presence throughout.

Streep, however, is the real star. She could always sing and does so pretty well here. She also flings herself almost bodily into the part, like Rafael Nadal into a rally. you can't say the same for Brosnan, whose acting is invariably better than expected but whose singing voice is only just on the right side of disastrous.

The Abba songs blend seamlessly into this melange of comedy, sentiment and farce. We have Money Money Money, when Donna explains her precarious finances, Dancing Queen as the three middle-aged women remember their days as Donna and the Dynamos, Mamma Mia! as Donna finds herself faced with her three former lovers and I Have a Dream when the thoroughly feelgood ending heaves into view. I could go on but you can see what I mean.

The whole is a bit of a shambles in essence, and always looks like a stage show plonked on screen by a director as yet unable to lick the boots of the makers of best screen musicals. And without Abba's remorselessly catchy tunes, it might have collapsed into a heap of mouldering clichés.

But I'll bet it works with most audiences, fed up, like Donna, with counting the pennies and finding they haven't got as many as they thought. for the admittedly none too cheap price of a ticket, they will be able to forget about everything and have a good time.

Never mind the variable quality - feel the sheer good-natured energy of it all. As they say in the theatre, this one will run and run.