I've picked up a Moto G +4G this evening at Tesco Extra Pengam in Cardiff for £139.
It is locked to Tesco Mobile, but using eBay and paying £1.69 for an unlock code I've got an unlocked one for £140.69. That is only 70p more than the out of stock unlocked one on their website, and with out any messing around with discount codes or having to wait for the delivery.
Sorry didn't ask if nationwide, but I can't see why it would be for such a new handset.
Used this guy for unlock: http://www.ebay.co.uk/itm/Motorola-Moto-G-Mobile-Phone-Unlock-Code-/111223239973