@cheesyboofs:
As wallabybob & Cry Havok said this has been discussed at length, here is a good start.
http://forum.pfsense.org/index.php/topic,13098.15.html
And
http://forum.pfsense.org/index.php/topic,11913.0.html
The main thing to look out for on mini-itx boards are that they usually come with cheep Realtek NIC's, take my advice and spend a little extra and get one with Intel GB NIC's, this is the one I've been running for a while now.
http://www.icp-uk.com/index.php?act=viewProd&productId=416
Then if you need extra network connectivity buy a cheap VLAN switch as I have, again covered in the post above.
At the end of the day only you can decide what will meet your needs, no one is going to say "ear mate buy one of these" as all you will do is say Oh that too expensive, or they don't sell that here in Greece.
Excellent! I will try to investigate further with all your help and advice. I will now more confortable with the idea of having an mini-itx system for PF.
Thanks again!