For closer your budget, this might be your best bet
http://www.overclockers.co.uk/showproduct.php?prodid=GX-123-HT
£8 more than your specced 5450, but better for gaming
http://www.overclockers.co.uk/showproduct.php?prodid=GX-123-HT
£8 more than your specced 5450, but better for gaming