Yup, you can get the cam box and the head off with the engine still in frame. Thanks for the heads-up about the XL600 though, I was wondering whether to pull my engine out or not. Looks like that's decided it for me.
Try Dave Silvers for the cam chain. He hasn't got them listed for your year but it's worth phoning, might well be cheaper than Wemoto.
Cheers,
Dave B