I think your spot on, a friend sent me a message earlier telling me that international Swift transfers are routed via a 'Central' bank, which apparently is where my funds are sitting now.
I've absolutely no idea what value this bank adds to the process but it's given me a great idea. I'm going to ban everyone from paying their council tax, instead they must pay it to me, I'll hold onto it for a week, enjoy the accumulated interest and then I will pass the payment on to the council after charging a commission to do so. As ludicrous as that sounds, it seems we allow the banks to get away with exactly this scam !