As the programme put it, Prom 16 had a "distinctly watery" theme. The BBC National Orchestra of Wales took its audience on a trip to the Italian and French rivieras, with a staycation in the form of Hugh Wood's thrilling Piano Concerto. It was a challenging programme, which showed in the orchestra's playing more than once, but it was nevertheless an enjoyable experience. It should be noted that the orchestra's originally billed conductor, Thierry Fischer, was unwell, and was replaced at very short notice by conductor Ryan Wigglesworth.

Having just finished writing The Apostles, Elgar set off, exhausted, to Italy in order to escape the British winter. After weeks of poor weather in Alassio, the sun finally shone, and he was inspired to write In the South (Alassio), a quasi-symphonic work in one movement (Elgar in fact regarded it more as an overture), which opened tonight's concert. As Elgar put it, the bold, expressionistic opening "may be the exhilarating out-of-doors feeling arising from the gloriously beautiful surroundings – streams, flowers, hills and distant snowy mountains in one direction & the blue Mediterranean in the other", with the middle, quieter sections representing pastoral scenes. The BBC NOW had a mixed result in the event: whilst the drama and sheer volume was there, there was an appreciable lack of ensemble between the main body of the orchestra and the percussion. Having said that, the quieter moments were the more successful, with the viola solo in the middle of the piece, taken by Göran Fröst, being exceptionally well executed – not a breath could be heard from the audience.

Next (after, of course, the traditional "heave... ho!" as the piano was set up on stage) was Hugh Wood's violent, vibrant and jazzy Piano Concerto, tonight played by wildchild of the piano world Joanna MacGregor, for whom the concerto was written. Combining stark dissonances, unusual instrumental combinations and more than a hint of jazz (the second movement is based on the song "Sweet Lorraine", popularised by Nat King Cole), it really showed off MacGregor's manifold strengths as a musician. Even when she was not playing, she was almost dancing on the piano stool; she clearly enjoyed the performance, and her enthusiasm rubbed off on the audience, which greeted the composer. Equally as challenging for orchestra and soloist, the BBC NOW could not quite match MacGregor's world-class playing, and, disappointingly, the ensemble issues resurfaced (added to that, there were some noticeable tuning problems between the brass and strings).

The English first half was followed by an all-French second half, with one work by Ravel and two by Debussy. Une barque sur l'océan ("A boat on the ocean") was the first of Ravel's self-orchestrations of his piano works; at its première in this form in 1907, it was criticised as "an inconsistent fragment containing not the slightest musical interest", and Ravel would later withdraw the score and refuse to allow its performance in his lifetime, conscious that he was composing in Debussy's formidable shadow. Quite what was so musically uninteresting about Un barque was difficult to see – highly evocative, its raging swells, quiet lulls and the often dramatic contrasts were largely handled well by a refreshed orchestra.

Three years later, in 1910, when Debussy published his first book of Préludes for piano, Ravel was particularly praising of La cathédrale engloutie ("The sunken cathedral"), believed to have been based on the legendary drowned city of Ys, whose bells continued to ring out beneath the waves. The original version captures this scene by dense block chords, which create the effect of muffled bells. Henry Wood's orchestration of the piece, which was last heard at the Proms in 1922, is loud and therefore less evocative, but his rich instrumentation and interaction between the various sections of the orchestra were handled well tonight.

The concert was rounded off with Debussy's La Mer ("The Sea"), a portrait of the sea in three symphonic sketches. The delicate build-up of the first movement, "De l'aube à midi sur la mer" was rendered by some sensitive playing. On occasion, througout the three movements, I felt that the joins between passages were not as smooth as they might have been, but the BBC NOW painted a picture of a rising sun, playful waves, and subsequent tempest especially effectively.

For someone who had been called in with two days' notice, Wigglesworth was an assured conductor, who glanced down at his score only on the odd occasion. It is a pity that his clear and confident direction – and violinist Lesley Hatfield's animated leadership – did not always translate into the orchestra's playing; it was impossible to tell whether this was the result of the last-minute change, or a more endemic matter. That said, Prom 16 was an enjoyable concert which left me dreaming of a holiday by the sea. Chance would be a fine thing...