Anyone who does ask here about what 5.1 system to get, people try to steer them clear of these all-in-one DVD based systems, as they are poor value really. It's a struggle to replace or upgrade certain parts and the amount of connections they have is abysmal.
Depending on what you have to spend, a Yamaha YHT199 package would be a decent choice. A AV receiver alone would cost you around £130-£150 minimum, so to get the whole lot for £200, is a good deal. Richer Sounds currently have the YHT199 for £200 down from £250.
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As for the tall tower speakers, they house very small drivers of very little quality. Proper floorstanding speakers would be vastly superior, but you'd be looking at £700+ for a 5.1 speaker package with floorstanding speakers. A good smaller speaker will sound much better than those tall tower things, but like the wattage rating, they are designed to attract the average consumer with the whole 'bigger is better' ethos. I suppose tall tower speakers are more convenient as well, sitting either side of the TV, rather than having to place smaller speakers on stands, a unit or a wall.