I don't have any experience with EG lasts, but from my research it's similar to the 82 last. I've been recommended to go with my 2030/trubalance sizing (i'm the same size in both) for the 72 last. So for me, I would go with an 8.5UK since I'm an 8.5 in 2030/trubalance. Since you have a narrow foot, perhaps a 10.5UK would work.
Will the Kentmere be available for purchase even if we didn't preorder?