HOW many of us have stood in front of a mirror, hair-brush or trusty air guitar in hand and warbled out our devotion to whichever God or Goddess of Rock that was reigning over the music industry of our time?

Rock Star is the story of a fanatically devoted wannabe who gets to live out this dream.

Set in the mid-1980s when stadium Rock ruled the charts, and British heavy rockers Steel Dragon were the metal gods of the time, Rock Star tells the story of Chris Cole (Mark Wahlberg).

Chris is an average Joe from working-class Pittsburgh USA.

By day he works as a photocopier repair man, but by night he fronts the State's leading Steel Dragon tribute band, Blood Pollution.

Notice that is a TRIBUTE band and not copy band. No-one would dare voice that slanderous label at Chris, who firmly believes that their higher purpose in life is to re-create the music of his idols, the greatest rock group EVER.

His obsessive encyclopaedic knowledge of Steel Dragon trivia stretches from dress and appearance - when lead singer Bobby Beers (Jason Flemyng) gets his nipple pierced, Chris gamely follows suit - right down to the authentic sound of his band which MUST be exactly the same as Steel Dragon (''You're not nailing the squeal,'' he complains to guitarist Rob (Timothy Olyphant) during rehearsal).

This passionate devotion is a source of amusement to his loving and strangely tolerant parents. But it is driving his fellow band-mates insane.

Fortunately, his creatively supportive girlfriend Emily (a convincing performance by Jennifer Aniston) is also Blood Pollution's manager and resident peacemaker when band tensions bubble over.

Initially delighted at living his dream, Chris is soon given a rude awakening - Rock is just a business like any other, and what goes on behind the scenes isn't always what it's cracked up to be.

Things come to a head when Chris is fired by the band who are sick and tired of his antics.

By a strange coincidence Steel Dragon have also kicked out Bobby Beers, their lead singer, for the same reason.

And wouldn't you know it, Kirk Cuddy (Dominic West) the lead guitarist, and brains of the band, has just come into possession of a video tape of one of Chris' concert performancesundefined

Hey presto Chris (re-named 'Izzy' for PR purposes) is now the front man in the band he once worshiped.

Too unbelievable you say?

Well before you jump on the train to unbeliever central, this is loosely inspired by fact.

The lead singer of a tribute band/office supply salesman from Ohio by the name of Tim ''Ripper'' Owens in fact did replace Rob Halford, the lead singer in metal band Judas Priest.

Director Stephen Herek paints a believable if clichéd picture of the 80s hard-rock scene as Chris and Emily are pitched into an insane lifestyle of sex, drugs, rock-n-roll, fast cars, screaming fans and self-destruction.

An innocent way out of his depth Chris, like Alice in Wonderland, must negotiate the innumerable pit-falls of his new life: drugs, alcohol, mercenary band-mates, sacrificing his creativity, gender-bending groupies, and his own increasingly destructive behaviour.

He is urged to embrace this hedonistic Wonderland and 'live the life' by someone who is on kidney dialysis between gigs because of years of self-abuse, a fact that doesn't seem to give him a moment's pause.

Meanwhile, the savvy Emily is left increasingly shut out and relegated to travelling with a bunch of mentally-challenged, prematurely aging wives and girlfriends, who submissively tolerate whatever the band toss out to them.

It is the early sections of the film that are the most enjoyable. At the beginning there is an easy sense of joy and energy, as well as an amusing sense of humour.

Rival tribute bands scuffle with each other without messing up each other's outfits, Chris' parents join in with the heavy rockers at Blood Pollution's concerts, and Steel Dragon's drummer wrecks a hotel room enraged because his wife runs off with Peter Gabriel.

Unfortunately, this is sacrificed in favour of a clichéd morality play as 'Izzy' hits bottom and realises that if things don't change he will loose everything that ever meant anything to him.

Fortunately, things are saved from becoming overly morose by Timothy Spall's performance as Mats, Steel Dragon's long-suffering road manager who must, by necessity, act as a liar, thief, drug-dealer, counsellor and therapist, in order to keep the band on the road, if not the straight and narrow.

The look and feel of the film are great and a fab soundtrack with contributions from top rock bands of the 80s: Bon Jovi, KISS, INXS, Motley Crue, Def Leppard and Everclear, as well as authentic offerings from Steel Dragon and Blood Pollution - they really perform original songs.

Performances are satisfactory, and despite it's moralistic shortcomings, Rock Star is an enjoyable and, for the most part, good-natured ride. Enjoy it while it lasts then forget about it.