It turns out it was VirWoX who delayed the transaction - I checked their support FAQs and.....
What is the "manual step" required to process some withdrawals, and how long does it take?
Withdrawals to bank accounts are usually processed on the morning of the next business day. While most withdrawals to PayPal, NETELLER, Moneybookers, and Bitcoin accounts are processed instantly, we manually check some of them for security reasons. They will be processed within 48 hours. In any case, you will receive an email confirmation when the withdrawal has been processed.
.... so apparently mine had been delay for security reasons. I received a confirmation email an hour ago that the payment had been approved and it's in my BTC wallet. It would have been nice of them to let me know it was being intentionally delayed for security checks in the first place.
Anyway that's the conclusion.... Bitcoin has been admonished of all responsibility