Right, after some buggering about with camE, and eventually replacing it with streamer from xawtv, I'm uploading two images onto the server.
Since one camera is at an odd angle, and the image needs to be rotated by 56°, which takes significant processing (on a not very powerful machine), it's taking around ten seconds to upload the images onto the webserver. Consequently, I've slowed down the page update rate slightly to 10 seconds.
If I can reorientate the camera so that only a 90° rotation is required, then things are likely to get a bit faster.