In the £500 price range, I think the Panasonic GS300 is hard to beat. (Unless you can find a good deal on a GS250, which is discontinued). Another good site (US based) for reviews is
http://www.camcorderinfo.com
If you look at their current ratings, you’ll see the GS300 is highly rated.
http://www.camcorderinfo.com/ratings.php
For video performance, the number of pixels isn’t significant (as long as there is 800k or so). PAL video is fixed at 720x576, i.e. 414k pixels. The number of “effective pixels” is less than the total so a camcorder needs more than 414k… but 800k is enough. What is more significant is the physical size of the CCD, and the number of them. Cheaper camcorders typically have a single 1/6” CCD; in the £500 bracket you can get either a larger 1/3” CCD, or three 1/6” CCDs. A “pro” camcorder will typically have three large 1/3” CCDs.
The Panasonic GS300 has three 1/6” CCDs (each with 800k pixels) – one for each colour. This generally improves video performance over a 1 CCD camcorder… though the physical size of the CCD, and other factors such as the lens, the DSP, are also significant.