Hi what catch pot size would I need to make a  carbon bamboo sun lounger? Would I be right in thinking the bigger the part being manufactured the bigger catchpot required ? 

Catch can only needs to be as big as the amount of resin you plan to let in it. You don't necessarily need a catch can at all, it's only job is to catch any resin that gets evacuated from your part before it destroys your pump. I myself have a 1L catch can, and it's never had a drop of anything in it.