An analysis of helium exhaust experiments on JET in the MkII-GB divertor configuration is presented. Helium is pumped by application of an argon frost layer on the divertor cryo pump. Helium exhaust in L-Mode and ELMy H-Mode discharges is studied by introduction of helium in gas puffs, and measurement of the subsequent decay of the helium content. In internal transport barrier (ITB) discharges, helium is introduced by beam injection and the helium replacement time is measured. In ELMy H-Mode, and with an optimised plasma configuration for pumping, τHe* ≈ 7.2 × τ Eth is achieved. For ITB discharges, the achieved τHe* ≈ 4.1 × τEth is significantly lower. The achieved helium recycling coefficient, confirmed by an independent measurement to be Reff ≈ 0.91, is the same in both scenarios. None of the discharges are dominated by core confinement. The difference in τHe*/τEth is instead due to the confinement properties of the edge plasma, which is characterised by TypeIELMs for the H-Mode discharges studied, and Type III ELMs for the ITB discharges. This difference is quantified by independent measurement of the ratio of the helium replacement time with a helium edge source to the energy confinement time.