1.8v DDR modules don't exist; they are 2.5v or 2.6v. The modules at clonline.com are DDR2, not DDR. The largest module size is 1GB low density (16 chips - 8 on each side of the module) and they are expensive (old technology always is).
Thx GhislainG, I missed this reply, I still haven't got round to buying it.
Just one last question, If I have 2 x 1 gb sticks and 2 x 512 mb sticks will they run in dual channel mode?
Could you elaborate on what you mean by "unless they are different"