Will fitting a combi boiler in a 3rd floor flat require scaffolding?

I live in a 3rd floor flat. I'd like to replace the existing Powermax SS 140 P boiler (located in a cupboard), with a combi boiler. There's a patch of external wall in the kitchen, beneath where the existing flue/intake exit. It seems an ideal location for a combi. Would fitting a combi require access to the outside of the wall? If so, would you have to erect scaffolding to reach the 3rd floor?