Neil74,
A 9mm might work out for you, it comes in 18, 20 and 21mm length's, but the 21mm is kind of rare in the states. Keep in mind that a semi has a different kick than a revolver because it uses the gases from firing to eject the shell, so a 38 semi would feel different than a revolver 38. I hope that didn't confuse your mind some. A 9mm is a nice round to shoot, at least for me and it is cheap to shoot also in 9x18. I do have 9,357,45,32, & 22 pistols and some black power ones too and the 22 and 9x18 are my favs.
Paul