I played 4 days a week from the age of 8 to 21. Have had a year off now, but I used to be one of the best players at under 18 level in Ulster. The racket is a tricky subject, but I'll do a quick run through for you.
Usually the more expensive ones are better suited to better players. They tend to be lighter at the head than cheaper ones because better players can generate more power through technique. Lighter heads also improve accuracy.
At your level, I'd say aim for a racket at around 85-90g. Look for a slight head heavy racket and possibly a little bit of flex in the shaft, which helps generate some more power and will reduce the risk of tennis elbow.
Now, the most important thing of all are strings and tension. For the sake of £15 a restring will transform a racket.
The higher the tension, the better the accuracy and power* but the sweet spot reduces. I used to play with yonex BG85 at 29lbs, but this was a restring every 2 months per racket pretty much.
Try Yonex BG 65Ti at around 21lbs. This will give you a good balance of power and accuracy and as you technique improves you can up the tension without sacrificing power. Don't try a tension too high too soon as it WILL give you tennis elbow.
*Power increases drastically up to about 23/24lbs, after which it falls off slightly, but tensions above this are used by players with good technique and as such does not suffer too much.
Try this one with a restring
http://www.centralsports.co.uk/shop.php?page=yonexd&product=5827
comes in at about £45
Hope this helps a bit
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