Hi Guy
Take you pick from any of the guns you mention. Just remember that they all have different characteristics.
The Alecto is recoiless and variable power, the HW 40 has powere to spare and both of these are accurate. The Gamo is rapid fire but is a little down on accuracy.
It's also good to remember that you can plink with a target pistol but not shoot good target scores with a plinking gun.
Enjoy
Target Bunny