Hi Rudi,
DV vs DVD: To decide which is best you need to consider what you will want to do with your "footage". If you don't want to edit on a PC at all, then a DVD camcorder has the advantage as you can shoot, finalise the disc (that's a step you do on the camcorder), and stick it in a DVD player. You can even do limited editing with the camcorder itself. The downside: in terms of quality for the money, DV models are generally better. That doesn't mean you can't get good quality with a DVD camcorder, just that a £400 DV model will generally perform better than a £400 DVD model.
With DV, other than connecting the camcorder to the DV, you pretty much have to edit. You can't give DVs to most of your friends, they may not be able to play it.
3 CCD: Putting it simply, the CCD (or CMOS) is the thing which converts the analogue real world into a digital image. 3 CCDs means there is one for each of the 3 colours, red/green/blue. All being equal generally this gives better colour than 1 CCD. But this isn't perfect - the act of splitting the signal into the 3 sensors can result in uneven compression, hue shifts, and reduced light transmissions. With CCDs, the (physically) bigger the better - and an affordable model tends to have 3 small sensors, which may not be better (or even as good) as another model with one larger sensor. Add to the mix CMOS vs. CCD... CMOS has many advantages over CCD, and there are models with a single large CMOS which outperform 3 CCDs..
Sorry if I've lost you, but the "bottom line": Don't get stuck with a hard requirement for 3 CCDs. Look at the overall performance of the camcorder.
Suggestions in your pricerange:
DVD: The only DVD camcorder I know of with 3 CCDs is the Panasonic VDR-D300. And it is a good one, but the cheapest web price I've seen is over £500, so it is out of budget. Very similar in quality is the Sony DVD505, which has a single large (1/3") CMOS. But it is also £500+... so what about in your price range? Real good deal on the Sony DVD404 here, £399
http://www.pcworld.co.uk/product.php?sku=306871 Every where else is £50 or so more. Has a single large CCD.
DV: Panasonic GS280 or GS300 - both around £420, or Sony HC96, around £400, or the Canon MVX460, around £320. The Panasonics are 3, 1/6" CCD. The Sony is a single, 1/3" CCD. The Canon, known as Elura 100 in the US, is good value, and performs well even if it only has a single 1/5" CCD. You could also consider the 3 CCD Panasonic GS180, though it's widescreen mode is not as good.