Space it still quite tight so the hoses need to be durable. Some people have managed to fit 75mm hose down the side, not sure how as I found 60mm difficult enough. The flimsy hoses from diy stores may not be able to sqeeze in the space without deforming. The original 50mm hose for the lower intake was all crumpled, it is extremely tight, I doubt you'd be able to get anything bigger than 50mm in that space.
The BMC hose I have were £8 and the pipercross was a spare item in my garage from another car, that was about £20 from halfords if I remember correctly. It also came with 2 alloy air trumpets which I've used for both modded intakes. The venairsport items are supposed to one of the best, but are expensive.