Is the diff on the PP a safety feature that could help me during normal driving or in the wet or is it just something which only comes into use when driven hard or on the track. Safety is important it worries be a little when reports say you need to bury the throttle in the corner to trigger the benefit. I have an interest in road safety during to my profession 
Not really a safety feature as such, it allows you to access more of the performance without spinning away the power through the unloaded front wheel... TBH, if you're seeing regular significant benefit on the public road... then let us know where you're going to be... so we can make sure we're not there

So, my understanding is that it is a "torsen" system... In my experience (similar torsen type diff on Integra Type-R), they're very good in the dry and damp/wet conditions reducing understeer and improving traction out of corners... Counter intuitive in snow/icy conditions.
Remember they only work under load. In snow/ice/wet mud etc they tend to lock (100%) and you will find that the car is very reluctant to turn... you need to come off the throttle, turn and then get gently back on the power.
Plate type diffs tend to me more tunable in terms of locking strategy (hence why the rally car I navigate in has a plate type diff) but require much more maintenance (a rebuild every few events) to account for the wear on the plates... This is why the majority of manufacturers who fit an LSD to road cars go for the torsen type as they require much less maintenance...