Hooray! It finally works, well I can get 160×120 video with xawtv anyway. Now to find out how to get a larger image and work out where to put the camera to get something vaguely interesting..
insmod pwcx-i386.o and hey presto! a slightly bigger image (still not 640×480 though).
Looks like this is an issue with xawtv as it works well using camE and fetches a full 640×480 image. Quality isn’t all that bad either – low light doesn’t seem to be an issue, the image just gets darker unlike the quickcam express which goes all horrible and grainy.