With help from people here on deeperblue and from various poking around teh internets, I got enough info to DIY my own weight belt and weights. I did a little write-up on it on my bloggy thingy. Just thought I would post up a link for people here. I probably got a load of things wrong, if so feel free to say so. it is all in the spirit of learning.
http://irishlostboy.blogspot.ie/2014/01/my-diy-weightbelt-rig-freediving.html
http://irishlostboy.blogspot.ie/2014/01/my-diy-weightbelt-rig-freediving.html