There's a lot of good advice on this thread, but be careful - some people may not need their drills to be as accurate as you. Once you've chosen the size and configuration of your drill - I think that runout is extremely important. The correct way to measure it is to put some round bar in the chuck and use a dial guage to measure runout. A quick and dirty way is to put some silver steel bar in the chuck ( as large in diameter as the chuck will take ideally) and push and pull it to see if you can feel slop - rotate the chuck a bit and try again. Turn the drill onto it's slowest setting and see if you can see any eccentricity as the bar rotates, it's amazing how many drills are visibly eccentric at this stage.
I looked around for a drill for ages and found SIP runout absolutely appalling; axminster, rexon, scheppach, and clarke were also bad. Jet were good The typical B&Q drills were pretty bad too. I'm surprised to see people reccomending clarke - it may be true that they've improved their quality or it may be that some people have low expectations of drill quality.
If you're drilling holes which need to be accurate then runout is important - if you're drilling holes and drilling bungs runout will mean a poor fit between bung and hole.
If you're only using a drill to do low precision work then it's not such an issue but if you think you might use it for precision work later - then try and get an accurate drill. There are a lot of good quality drills available used meddings, fobco, record power, all seem to have a good reputation, and quite often appear on ebay at your price.