This behavior is to be expected, as the system must maintain its presence on the network in order for other devices to be able to locate your Home Share.
With Wake on Demand enabled (see below) and your Mac in sleep mode, your Mac will occasionally wake for a brief time, without lighting the screen, in order to maintain active shared service registrations with the Bonjour Sleep Proxy. On some Macs, sounds from the optical drive, hard drive, or fans may be heard during these brief periods. Note: Removing a sleeping Mac from the network will automatically remove its registered shared services from the Bonjour Sleep Proxy.
Many thanks for the links, although i was aware of the sleep proxy and its uses. The problem i'm having does seem to be related to this, although the key difference between what i am (or was) experiencing is the definition of 'occasionally' as mentioned on the page you linked to.
What i was experiencing was the mac mini would go to sleep then 60 second later it would stir, as if being woken to reregister its services with the sleep proxy, then it would go back to sleep. Then around 60 seconds later it would do this again, and so on and so forth until it was fully woken in one way or another.
Now i do seem to have made progress after digging around a little further. I did figure out that it was a bonjour service/ or device that was causing the mac mini to stir And as i mentioned in my previous message this behaviour would cease if itunes was closed or home sharing was turned off. So the only thing on the network that was connected to this was my 2 apple TVs. As a test i unplugged both boxes and put the mini to sleep again. Then i waited and waited and the mini stayed soundly asleep.
I have since plugged the 2 ATVs back in, one at a time, and the mini now seems to be sleeping for around an hour before it wakes, presuming to do the sleep proxy service thingo.
i'm just running another test to prove to myself that it is actually back to a more normal state with both ATVs plugged in, so fingers crossed.
if anyone knows, does this now sound like a normal setup with the way the sleep proxy works?
i suppose i should have done this at the start, but i have 1 airport extreme, and 2 ATVs (and few ipads, iphones and the like all onthe network), if that helps.