Breva rear wheel removal and corrosion

Looking for the cause of a slow pressure drop in both tyres I discovered that it was leaking from around the valve stems, and when I looked inside I discovered flaky corrosion. I was hoping to remove enough to get the tyre to seal properly again and deal with it properly when I have to change the tyre, but I just can’t get a good seal so I want to get the wheels refurbished. My problem now is that I can’t get the rear wheel out! The left hand silencer just won’t budge, it’s like it is welded to the pipe. I could probably get the wheel out if I could get the caliper out of the way but I can’t see how to do that as the locating bolt looks like it has to be unscrewed from the end which is hidden by the silencer. I’d like to get it done while the weather is reasonably good, any suggestions?
Also, any recommendations for a place to get the wheels refurbished? Has anyone else had a problem with corrosion inside the wheels?

perhaps a strap wrench on the silencer to rotate it a little at a time, there was a recall on the early bikes, and the mounting bracket had to be drilled to move the pipe forward
it may be that somebody has used a sealing compound and that is causing it to stick
perhaps use a small flat ended chisel and a small hammers to force the silence backwards ?