I'm going to replace these few missing bricks so I can chuck a couple of little shelfs up here to make better use of the space.  



It might be a daft question, but if the rest of the wall is built with lime mortar, is there any issue with just using a sand/cement mix for just doing this one little repair?  The bricks were removed when they were messing about with the roof back in the 90s.  Its the dividing wall between us and next door, I'm guessing its 2 bricks thick, I can't see why they would have built it any thicker than that

Cheers