ok im a way off this point yet but does any one have any idea whe is a good time to 'make yourself known' to potential postdoctural supervisors? a few months before expected to finish the PhD?

I think you should start to apply for a posdoctoral position(s) as soon as possible. Good luck

Perhaps your current supervisor would know of potential post-doc supervisors. I would say a few months yes, because the deciding factor will most likely whether they can fund you, and getting grants can take a while.

I was told that start applying even 1 year before you finish your PhD won't hurt. Some postdoc scholarships (for example those at the Oxbridge colleges) are advertised in October-November for start in September next year.

the second you start your phd :D it's always good to network ;)

do you think most people secure them from finding out about projects by word of mouth / through their supervisor etc rather than advertised posts?

i think word of mouth def plays a part in some circles