I've been through this myself recently and have bought both pellet and blowback BB pistols. Either can be used for target
shooting. Some will obviously perform better than others.
Your budget will get you one of the decent blowback pistols and if you go secondhand I'd consider Umarex's Walther CP88, Beretta 92FS, or Colt 1911A1 all 8 shot pellet firers and all serviceable with good spares backup.
Plenty of good friendly advice on here http://www.umarexboysclub-forum.co.uk/