He was much the same for about a week, and I was glad to think the condition wasn't getting any worse. I posted on a couple of forums and facebook groups about him, and was advised that what I was doing (or not doing) was okay as long as the bird seemed well otherwise.
At the beginning of the second week, I noticed that his wheeze was more pronounced and more frequent, so I was a little bit more concerned at that point. I took a video of him making the noise and posted it on my usual poultry haunts.
A couple of people suggested dosing him with vitamins in the water (which I had already commenced the week before) and trying some garlic oil or getting him an antibiotic or trying to nebulise him with a product called F10 SC.
Not having a nebuliser, that option was impractical, and I couldn't find any local feed barn that carried the antibiotics I'd need.
By now, I had tried vitamins in his water, and had given him some naturopathic tissue salts (Combination 12) to help him fight off the infection on his own.
Finally, lacking any ideas for what else I could do, I mixed up a wet mash of vegetables with oatmeal, molasses, garlic and oregano and fed that to him. He wolfed it down with great gusto and his wheezing stopped almost immediately! Apart from a small raspy wheeze if he gets stressed now, he hardly wheezes at all anymore.
I am putting it down to one of three possibilities.
1. The illness had run its course and he was going to get well anyway
2. He had something lodged in his trachea and the wet mash helped to dislodge it
3. My naturopathic and organic methods gave him the support he needed to fight off the infection
I think it could possibly be a combination of all the above. I'm just glad that he seems better now.