I use a crossman laser - probably the £25 one you were talking about. I got it for about that from the sponsor.
Its a good laser, fits on the rails on my beretta fine (although the 'lock' is in the wrong place) and its fully adjustable obviously. It's more accurate than the pistol when adjusted correctly and I use it for increasing accuracy in target shooting and easier plinking - allows shooting from the hip and stuff which is nice.
On a side note I also use it to see if the barrel is obstructed after a miss fire; shine it down the muzzle and pull back the slide to expose the ejection port - if I can see the beam projecting through the breach its clear, it not there is a pellet in the barrel
http://i9.photobucket.com/albums/a62...h/IMAG0413.jpg