Worth it to upgrade to Rega P3?

My advice is your key words:"I am very happy with it"
Changing something you are 'very happy' with is a BIG MISTAKE!
The vast majority of audio nuts cannot find 'very happy' let alone 'content', or 'resignation'.
Stick with what is making you happy. Really! you have what EVERYONE is looking for. I suggest you hang on to it.

Consider upgrading to a suspension system of isolation.

Go to Machina Dynamica website, then Promethean Springs. Somewhere there is an article on the effects of vibration.

I use 2 sets-one for my amp the other for my CD player.

check out a P-5

I agree with Elizabeth..........Your equipment should put a smile on your face when you listen to your music. If you are "very happy" with your Rega P1, relax, spin those LP's, and keep on enjoying.
Now, if you want to upgrade as a way of exploring what the "next level" of quality analog will give you, the P3-24 will probably enable you to hear more of an improvement than going to the P2. I'm personally thinking of upgrading to a P5 from my current P2 rig, and I do enjoy the "Rega sound." Good Luck, and Happy Listening !

great advice, thank you very much. :)