Having tried the shoes for fitting, you'll have to return your monk shoes to SL for doing patina, won't you?
I intend to buy a raw derby of SL for patina as well, so when you have yours finished, please post some pics :)
Although I don't have any 199, (I just have 174, 198 and 206) I personally think you don't need to size up. Normally I wear 8D US and my boot 7.5UK in 198 fit me well, a derby 7UK in 206 is tight a little bit and a pair of boot 8UK in 174 (which is slimmest I think so) is loose a little that I have to put an insole inside my boot.
Sent back the day after they were received
One thing I neglected to ask (although I don't think they would allow), was to send ONE raw monkstrap in 6.5UK, and ONE of theraw oxfords to me in 7.0UK, so that I could kill two birds with one stone in terms of sizing. But, that's probably a pretty rude request, hah.