The Coronation of Popea, Coliseum, London<br/>The Fortunes of King Croesus, Grand Theatre, Leeds<br/>Seraglio, Theatre Royal, Glasgow

Though Monteverdi supplies plenty of music about sex, ENO's 'Poppea' fails on the intimacy factor

Time was when even The Pearl Fishers was the province of paunchy Caucasians in supersized sarongs. Now everything from Adams to Monteverdi comes with a liberal dressing of tiny Javanese dancers.

"Gosh, that's pretty", you might think, vowing to retrieve your gym membership card from its hiding place under the pile of empty pizza delivery boxes. Only later might you wonder what all this prettiness has to do with the work you were meant to have seen.

After Chen Shi-Zheng's decorous East-West Orfeo, English National Opera knew what to expect from The Coronation of Poppea, the second of four Monteverdi productions he is scheduled to direct. Where Orfeo was spring, Poppea is summer.

Hence the setting is the prow of a yacht, on which Kate Royal's bikini-clad courtesan stretches langorously, sipping post-coital cocktails while having her toenails buffed by Christopher Gillett's dyspeptic Arnalta. Behind them is a video of a coral reef, with sea anemones puckering and pouting like starlets on a casting couch.

With Ottavia (Doreen Curran) resplendent in purple stockings and suspenders on a giant, glowing sponge, Amor (Sophie Bevan), Fortuna (Katherine Manley) and Virtue (Jane Harrington) wrapped in day-glo cellophane, and the Orange Blossom Dance Company striking tantric poses, Poppea is certainly diverting. Yet it is also unmoving and uncentred.

Lest this sound like another Carmen, the death of Seneca (Robert Lloyd) is so powerfully translated in flora&faunavisions's video projections that one can forgive the pseudo-erotic scuba-diving frippery. The production looks expensive and provides a degree of spectacle, though it is debatable how important a factor spectacle is in this intimate examination of lust and ambition.

What directors Chen and Sally Potter share, however, is a heroine who remains literally and figuratively at a distance, and a hero whose personality is under-explored. Though Monteverdi supplies oodles of music about sex – the dull ache of too much of it, the sharp pang of needing still more – Royal is as minty clean as a toothpaste advert.

This is not the first time ENO has put a magnificent singer in the wrong role. (Think of Emma Bell's earnest Violetta and Alice Coote's muted Carmen.) But dangling Royal from a swing does not conceal her discomfort in these musky, low-pitched ariosi. Instead of giving us a Cécilia Sarkozy, capable of bringing a leader to his knees, Chen offers an air-brushed Elizabeth Hurley, with a wedding to match.

As the diminutive despot Nero, Anna Grevelius is quietly compelling, but her carefully detailed singing is drowned in the production's incidental luxuries. Even Lucy Crowe's energetic Drusilla – a re-hash of Handel's Poppea – is upstaged by Lloyd's Seneca and Diana Montague's Venus, who make the younger singers seem fey and frivolous.

In the pit, Lawrence Cummings presides over a fat, oily seam of chitarrone and lirone but lacks the confidence to let them have the last word, adding a sugar-frosting of strings and recorders to "Pur ti miro", the iconic duet that may or may not have been written by Monteverdi (Benedetto Ferrari is a another suspect). Much of the rest has been cut, though not enough to make Tim Mead's glottal-happy Ottone appealing. It's glossy. It's glamorous. But this Poppea has more to do with Grazia magazine than the 17th-century ideal of grazie.

Up in Leeds, The Fortunes of King Croesus would benefit from a touch of Chen's deodorised opulence. Tim Albery's staging is thrifty to a fault, with little that glisters and even less that is gold.

Reinhard Keiser's score has some peachy arias for Elmira (Gillian Keith), later plundered by Handel, and an unusually high incidence of ensembles for an unusually large cast. Paul Nilon brings authority to the underwritten title role, male soprano Michael Maniaci adds novelty, and the orchestra of Opera North has adapted well to the short bows and long trills of baroque style under Harry Bickett. Heavily edited, it still feels like a long evening.

When Tobias Hoheisel and Imogen Kogge described their production of Mozart's Seraglio as "a black box with a sand-pit" on Radio 3, my heart sank. After a tartan-free Lucia di Lammermoor, can Scottish Opera afford to deprive its audience of Janissary bling?

In the end, this was the most intelligently directed of this week's new productions, though not the best sung, the best played or the best conducted. The polyglot cast seem mildly scandalised by David Pountney's demotic translation. (Note to singers: the word beginning with P rhymes with "this" not "these".)

Given a choice between Thomas Gerber's swoonsome Bassa Selim and Eric Laporte's stolid Belmonte, I doubt I'd be as faithful as Julia Borchert's dour Konstanze or as keen to escape as Rebecca Bottone's perky Blonde. Still, Dimitry Ivashchenko (Osmin) and Eberhard Lorenz (Pedrillo) were amusing company, and I'd be happy to split a bottle or two of wine with them next time I'm stranded in a conceptual sand-pit.

Further reading Tacitus's account of Poppea in 'The Annals of Imperial Rome' (Penguin Classics)