If the 30 day rule does apply - would it apply if you sold the gold and then repurchased it in a different domicile to the UK like the USA or Switzerland through the same company like Bullion Vault?
Yes; the asset purchased is identical to that sold.
Is there the possibility that HMRC would want to treat gold on BullionVault separately for each of the vaults that BullionVault offer, ie put them in separate Section 104 pools for CGT purposes? For example on BullionVault we can buy gold stored in the London vault and gold stored in the Zurich vault. If these were in an amalgamated Section 104 pool then we could sell London gold one day and buy back the same amount of Zurich gold the next day (for generally very close to the same price) and thus obviate the '30 Day Rule' for CGT.
In TCGA92/S104(3) it says fungible assets should only go in the same Section 104 pool if they were to be treated as a single listing in the event that they were placed on a recognized stock exchange. However would that apply in this case?
BullionVault do actually have separate listings for London gold and Zurich gold on their live order board. The difference in price of the gold between the different vaults is generally very small, typically a 0.1% to 1% difference. Though in principle there is no reason why the price difference may not become much larger under certain circumstances. In the contract notes issued by BullionVault they always specify the vault from which the gold was purchased or sold, for example "Buy 0.098 kg @ 30,190 GBP/kg Fine gold kilos in London vault".
So the question is are these two more fungible than they are not fungible, and what view would HMRC take.