Many thanks. It has been suggested elsewhere that the first one isn't as sharp as it might be, and on reflection I think I chose it as much for the car as the image quality - I have a much better image but of a more modern car that I somehow don't like quite as much. I sometimes forget that when I post for critique on a photographic site, it's different to when I post shots on a motoring-related forum. For example now I look at it, that last one of the Vulcan is only quite good because it's on the side - I have a much sharper image, but the plane is flat and it's just not as interesting.
As you can see I've been trying to practice panning shots, and I'm still finding issues where it's very hard to get as much of the vehicle in focus as I would like, unless I get into a much faster shutter speed and then lose the background blur and basically turn them into parade shots. Still trying to decide where the issue lies - the relatively low-end lens (bought for flexibility between track and paddock more so than anything else), the camera body, or me. Possibly the latter as I haven't shot any moving stuff since the beginning of May, and before that since last August, so plenty of time to lose the feel for it, if indeed it was ever there. Must look out for some track days at Oulton Park, possibly a source of free practice.