Small builder. If it's on the ground floor you won't need scaffold.
Rather than chiselling out bricks, I'd recommend a Core Drill that will make a neat round hole. Start from the outside for undamaged visible brickwork. It will make a messy broken crater on the far side when it breaks through. Decent workmen prevent this by going round to the inside to finish, this is especially important on a cavity wall to reduce rubble falling into the cavity.
The hole should be lined with plastic duct. This is especially important on a cavity wall to prevent damp getting into the cavity.
In a cavity wall, the cavity should be packed with a mineral wool sleeve as soon as the hole is made to prevent rubble or draughts.
The hole should be drilled with a slight slope towards the outside so any rain or condensation will run out.
The builder will suggest a 105mm hole. This is because it is the size used for soil pipes and cheap little fans. But as it is a kitchen I recommend a 150mm hole. Thus will be suitable for a decent size kitchen extractor in future, or a modern cooker hood.
On the outside I recommend a cowl vent which throws off rain and wind and does not rattle annoyingly like the ones with little horizontal flaps.
The core drill is very heavy and powerful. It needs a strong experienced worker standing on a secure platform. It can be hired. Builders and plumbers will have one but possibly not the 150mm core.
A low quality worker will grumble about these points and tell you nobody else bothers about doing a proper job.