Thanks Kathy. Luckily, I'm an antiques restorer in 'real life', and I'm so used to fixing things that it never occurs to me not to at least try.
I'm pleased to report that Brian the Oxycon (Martin Tuffnell apparently names his refurbed oxycons and puts a name sticker on the top!) is working beautifully and is actually a lot better than when I first tried - much hotter flame and the flow indicator is holding rock steady at 4 ltrs/min, where it was bouncing up and down before.
I have my beautiful candles back, so a result I think!! Now I just have to re-learn everything to cope with the higher temps!