Heres a belated update for you guys. Its been a couple of months since Ive had the work done now, and can report that all is well and the car is running as it should
It all started from this thread http://www.350z-uk.com/topic/92590-hr-potential-oil-pressure-problem/page__st__60
And then, after seeing Roscoes results, I concluded that mine was suffering the same, so went ahead and got Mitz and Andy @ Cougar Store to carry out the work for me. They did a fantastic job, and I can show you some photos of the work in progress.
Love this picture
You can see the original paper gaskets in the photos, and where the oil was leaking by internally. These have now been replaced with the later Nissan steel reinforced gaskets.
Thanks again to Roscoe for pointing me in the right direction, and to Mitz and his team