I had the same problem as you. I would not size up. Keep the size. If anything, you may size down one half. But I would keep the size the same for the first pair. I will be sizing down in the future. Here's what I have/had Based my fitting on a great fitting 11.5D US Cole Haan (we all start somewhere, right?) Inca - 10.5UK, tons of toe room, a little room on the sides. I thought this fit great until.. Simpson - 10.5UK - This is how a shoe should fit, for me at least. Same amount of toe room, snug on the sides. Uetam - 11UK - Got these before through Skoak and didn't like the shoe and the fit felt a little big. I was terrified to do it but I sent them back and sized down half. Uetam 10.5UK - Fits great all around. But since there's room in the toe (which there should always be) and the opening is so large, my foot slides forward a little and the entire shoe slips off. I don't even need shoe trees to put these on. Future Plans: Uetam 10UK - Will be more snug on the sides but not unreasonable. And the slippage should be mostly gone. Rain - 10UK - Sizing down since it's so damn large everywhere, just like the Inca Simpson 10.5UK - Since it's not larger and it's not a loafer, sticking with the usual.