can anyone tell me the difference in a p5, a 5g and a 5gm?

The 5GM is what RWS imports to the US, which is the same as the Diana P5M other than the Diana labelled guns don't seem to have a safety(at least in Canada). I think they are both built on the same frame as the 5G, only they have a muzzle break with fibre optic sights, and maybe a bigger spring to make the extra power.
If I could go back in time, I think I would choose the plain old 5G over the magnum pistols. Sacrifice some power for a smoother shot, and also for the better sights. I do enjoy my Diana P5 Magnum alot, and it is pretty accurate once you figure the thing out. Just my 2 bits.

Mulby

 Mulby,

 The Magnum came in with a lot of fanfare, some misquotes and has always been a sorta contriversial purchase. Power is VERY good! Accuracy potential is too, and with a lot of pratice, should fare very near the lower recoiling basic Model-5.

 Sights are important, andsometimes make or break a pistols reputation. Webley has suffered from poor sights, yet once learned, the pistol can shoot pretty impressivelly. BSA went through a real cut-low, when Beeman declared the Scorpion to be less accurate than nearly everything, however presonally,and over a rest/open sighted, I have stuck 2 Match pellets into a 50 yard 12 ga Hull (which I keep on my Desk) with my .177 Scorpion! Even guns like the RWS Model-9 can be shot well (for some reason(?) I can hit with that model, offhand(?). Guess that's what makes it intresting to own more than one Springer!

 Indeed a nice shooting pair would be both a 5-Magnum and a 5 Standard model! Perhaps buying one slightlly "Used" could help this?

  Recoiling Springer Airpistols are without a doubt the most difficult airguns to master! You can easilly go theu a tin of pellets and still be shooting wide groups... I have found each one needs maybe a loose finger somewhere, maybe a stong thumb alongside in a 2 hand hold, or even hanging ones wrist over and ahead of the rest... My best advise is try everything (even the unorthodox), and bingo, you can find the trick!

 Heck, I just love my old Daisy 717 and my Marksman 2004! They're so easy to shoot!

 One pistol that gets overlooked is the CZ-TEX. It is a superblly accurate .177 Target pistol! Velocitys are lowish, and the Pistol was intended for 7m indoors, but good adjustable sights, a very good BBL, and decent tuneable trigger make it a looked-over winner!

 SHooting springer Pistols, especally powerfull Springer Pistols is an art! Accomplish it, and you'll really suprise mainlly yourself, and surely your friends!

 ZVP

You're right, that P5 was a long learner. I ended up finding a good consistent grip and the right pellet for it and haven't looked back. And being just over 5fpe makes it alot of fun to plink cans out to 30 or 40yds, and it does pretty well on paper to.
I've got so many rounds through it that I'm sure the spring is getting tired, but as long as it shoots at this power level consistently I'm leaving it as is. I'll do the spring and seals together when the time comes.
The one and only Webley airgun I have is the Hurricane, and it was a challenge to learn aswell. I must say though, that it must be one of the Webley's that won out in the sights deparment because I think they are great. A nice hooded front post with thumbwheel adjustable rear. It's lots of fun to shoot and accurate if you hold it consistently, mine seems to shoot really well with Gamo match wadcutters, cheap and effective.
What I've really been playing with alot lately is my HW50s. For the money it's a gem, and I won't hesitate to try it in .22 next time I get down to Illingworth's. My .177 is only 5 or 600 rounds old and it's really accurate and quite smooth making around 11fpe with Exacts. I will be getting a couple of Williams peeps in the next while and I hope one of them will work well on the 50s, the Anschutz that I have on it now works great, but it seems so big on the rifle.

I hope all is well with you and your's, happy holldays.

Mulby