WILLIAM Walton was the sort of English expatriate who rejected and retained his home culture in equal measure. You hear it in his later scores, which temper bristling English ceremonial style with lazy Mediterranean balm. And you find a surviving token of it at the composer's home, a tourist attraction on Ischia in the Bay of Naples. Walton died in 1983, but his wife Susana maintains the exotic gardens and a small museum of Waltoniana; as you amble through this paradise of tropical vegetation, fountains, waterfalls and mountain views, you'll very likely hear familiar music filtering through the trees. It's Walton's coronation marches coming from the tea-house: Orb And Sceptre, Crown Imperial relayed in all their ermine glory as the scorching Italian sun beats down.

I mention this because the annual Walton Foundation Summer School has just taken place on Ischia, in its inimitably Anglo-Italian way. A sort of house party with a purpose, it brings together young singers from Britain and Italy with proven vocal skills but little stage experience, and coaches them in the theatrical aspects of opera performance. You might ask what that has to do with William Walton. It's a good question: he wasn't specifically an opera composer. But the later years of his life were dominated by one big stage work, Troilus and Cressida, which in its time was deemed a failure and caused him considerable anguish. As he looks down from heaven it must be comforting to see that Troilus has been rehabilitated by Opera North's recent production and superb recording for Chandos - which has just come out, caught with immediacy and brilliance under the conductor Richard Hickox.

For those of us left on earth, the pleasure of the Walton Foundation school is the stand it makes for British finesse in the congenitally rough- and-tumble world of Italian opera. The music director is Martin Isepp, former head of music staff at Glyndebourne. The production director this year was Ian Judge, whose clipped, acerbic wit softened by boulevardier largess gives his work a distinctive colour. And the result was a Cosi fan tutte of memorable sharpness, especially from the Italian mezzo, Gabriella Sborgi. She sang Dorabella with an easy accomplishment that should find her instant work on the world circuit. None of the British contingent was so obviously ready for the world to see and hear. But Sidonie Winter's fulsome if severe Fiordiligi, Ivan Ludlow's matinee-idol Guglielmo, and Christoph Wittmann's heartfelt Ferrando all had definite promise. More importantly, they grew in stature from night to night, edging toward that magical point where stage performance becomes an intrinsic part of the process of singing, and not just something you try to remember to do between arias.

Back in England, there were more young singers of promise at Broomhill, the Victorian pile near Tonbridge, Kent, which has become a summer home for country house opera with attitude. Less elegant, more radical than Glyndebourne or Garsington, it packages new, experimental work with one big established piece that sells on the name of the director; this year the director is Simon Callow, who has worked in opera before, though not extensively. What he does here is a conscientious Il Trittico, which attacks the problem of making Puccini's three mini-operas feel as though they belong together by setting them all in turn-of-the-century designs - including Gianni Schicchi, which becomes a comic take on one of Callow's own films, A Room With a View. They also share a common set which adapts cleverly but rather fussily to each piece, choking the small stage with detail. Beautifully lit by Simon Corder, it all has a rich, decorative opulence that threatens to overwhelm the performances. But the singers fight back - and with a vengeance, because there are some astonishingly good voices in the casts. Christine Bunning soars heart-rendingly into the stratosphere as Suor Angelica; Anthony Marber makes a sober but strong Schicchi; and there's a striking tenor in Il Tabarro called Antoni Garfield Henry, whose Broadway background is too obvious in the voice (as though he'll slip into a Gershwin medley any minute) but provides a gloriously direct and open sound. With cultivation this could be a major operatic talent.

My reservations are that Callow surrenders too easily to the sweetness of these little operas (Suor Angelica is endearingly misprinted in the programme book as Sour Angelica. If only ...) and that Charles Hazelwood's conducting is more show than substance (with pedestrian tempi). But the cut-down orchestral sound from Hazelwood's chamber group Eos is impressive; and in general terms this Trittico argues for Broomhill as a quality enterprise. Last year it was nominated for a Prudential Award but didn't win. It has just been nominated again, and must be a strong contender.

Visitors to London this week included the Sydney Symphony Orchestra, over for the first time in25 years and making its voice heard at a critical point in Australia's cultural realignment from Europe to Asia. The orchestra's Prom on Wednesday was in fact an uneasy mixture of Strauss, Canteloube and the Australian composer Richard Meale, whose Very High Kings is distinctly European: a love-letter to Messiaen and the French avant-garde. But there's no doubting the potential of the SSO to become a very interesting ensemble underEdo de Waart. It hasn't yet the cohesive richness of sound to pull off Strauss's Alpensinfonie, a risky piece, but Canteloube's Chants d'Auvergne had an elegant transparency that framed Yvonne Kenny's radiant singing to perfection. And the orchestra certainly has spirit. "Waltzing Mathilda" as an encore went down well with the antipodeans in the audience.