Thank you for your help. I'd forgotten about the Old Man Mountain option - their Cold Springs front rack that uses the front QR skewer as a mount looks a far better option than the Surly.
Thanks for the Nitto suggestion too - but I've got a Nitto already on the front of my other tourer and I don't have canti mounts on this project. The Nitto is a beautiful bit of kit and amazing value for money.