Im toying with the idea of fitting one of these CPD valves as im pretty sure my breather is totaly screwed has anyone fitted one of these valves and has it made any diffrence????

yep and it works, it's just a cheaper and easier way to fix the problem

Does the engine run any better? What do you get? Better economy, or a bit more power?

Maybe a few less drips of oil after a hard run? I'd like a verdict of how worthwhile it is also please.

I have quite a bit of oil getting into the air clean which is why I ask as been led to believe that the breather being stuffed would do this!?

Before replacing the oil breather, do a compression test to get a picture of how much compressed air is passing the piston rings. If compressed air hits the crank shaft housing (sump) even new original oil breathers can't cope with the pressurised air. It may be OK at low idle but not at high revs.
In other words it may not be the oil breather but too much pressure.

Well, my 2cv has done 185,000+ miles (115,000 in my owership), on original, untouched engine, so I would hazard a guess that the rings are past their best.