Boiler for flat with boiler location in middle of property

Hi - want to check whether there is a gas boiler that can be situated in the airing cupboard (not on external wall) whereby the flue can run horizontal in the void and inspection hatch. I have a Combi at the moment and the flue had to be boxed in with a hatch as it had to run at an angle - runs across the edge of the bathroom which is just awkward. There are other flats in the block that have the same boiler location and it looks like they just have a hatch in the ceiling to inspect the flue, so wondering what gas boiler system this would be