Ian,
Thanks for that - sorry I should have been clearer - I disabled Wake on LAN settings in BIOS and in Device manager...
HOWEVER
Your post prompted me to check device manager again and I discovered this:
Picture 1) The setting I had previously disabled - and the one I think your post refers to:
BUT then I found this in the driver settings - I presume it's a similar option, but it was set to "Enabled" which I'm guessing is NOT what I want!
So I'll give that a go...

Thanks for the reply
EVGA 680SLi Motherboard, Intel E6600 LGA775 3.4GHz OC'd, ATI Radeon HD 5850 1024Mb, 4Gb Corsair XMS C4 2x Matched Pairs, Samsung Spinpoint's 740Gb RAID 0 SATAII, Antec Three Hundred Case, Windows 7 Home Premium.