Looking at the prices, I assume you're looking for a budget camera. Fuji and kodak make decent budget cameras. I would stay away from the more expensive super-ccd Fuji cameras though. Olympus and Canon make the best cameras. Their cheapest ones prolly start at around £150.
I would totally forget about the zooms you're talking about with "preview" and "playback".
The manufacturers advertise the zoom as either "optical" or "digital". Optical zoom is real zoom, as in the lens is actually adjusted to go more telephoto (zoom in) or more wide-angle (zoom out). This retains all the quality as in there is no fakery in the picture.
Digital Zoom is just interpolating the pixels to make the picture bigger without getting extra detail. So doing this will result in a poorer quality. Going too high in digital zoom will result in a pretty blurred up picture.
Having said that almost any camera with a ccd (never get a cmos based camera) will produce good enough pictures for personal/funtime on-screen viewing (email, web etc.) Some cheap 2mp cameras will even produce semidecent 6x4s. Anything beyond that, I would think about what I need, where I'm willing to comprimise. etc. etc.
Hope this helps.
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