@ Silverdemon - Thanks once again for your help, option b would also give me more scope for modding aswell, given that lots of splitting / connections would be needed and what you say about the different flows through each of the blocks would make sense.
Again thank you for your input. +rep
@ Zephik - I never even thought of using 1/2" tubing between the res, rad and pump. What a great idea, thank you. That should help even out the flow. +rep